Protective sheet for solar battery module, method of fabricating the same and solar battery module

ABSTRACT

A protective sheet for a solar battery module comprises a weather-resistant sheet ( 1 ) of, for example, a fluorocarbon resin, and a deposited inorganic oxide thin film ( 2 ) formed on one of the surfaces of the weather-resistant sheet ( 1 ). A surface-treated layer ( 3 ) is formed in the weather-resistant sheet ( 1 ) to enhance adhesion between the weather-resistant sheet ( 1 ) and the deposited inorganic oxide thin film ( 2 ).

TECHNICAL FIELD

[0001] The present invention relates to a protective sheet for a solarbattery module, a method of fabricating the protective sheet and a solarbattery module provided with the protective sheet. More specifically,the present invention relates to a protective sheet for protecting thefront surface or the back surface of a solar battery module, excellentin properties including strength, weather resistance, heat resistance,light resistance, wind endurance, hailstorm resistance, chemicalresistance, moisture resistance and soil resistance, and having veryhigh durability and protective ability; and solar battery moduleemploying the protective sheet.

BACKGROUND ART

[0002] With an increasing rise in awareness of environmental problems,solar batteries as clean energy sources have attracted a great deal ofattention. Various types of solar battery modules have been developedand proposed in recent years.

[0003] Generally, a solar battery module is fabricated, for example, byfabricating silicon solar cells or amorphous silicon solar cells,superposing a protective sheet, a filler layer, a layer provided withsolar cells, i.e., photovoltaic cells, a filler layer and a backprotective sheet in that order in a laminated structure, bringing thosecomponent layers into close contact by vacuum, and laminating thosecomponent layers by a lamination process.

[0004] The solar battery modules were applied to pocket calculators inthe early stage of solar battery application and, subsequently, began tobe applied to various kinds of electronic apparatuses. The field ofcivil application of solar battery modules have rapidly been spreadingin recent years. The most important object of the solar battery moduleapplication will be the realization of large-scale, concentrated solarbattery power generation.

[0005] The presently most common front surface protective sheet for thesolar battery module is a glass sheet. Resin sheets, such asfluorocarbon resin sheets, have become notable in recent years and thedevelopment of resin sheets is in rapid progress.

[0006] Resin sheets excellent in strength are the most commonly used asthe back protective sheet for the solar battery module. Metal sheetsalso are used as back protective sheets.

[0007] Generally, a protective sheet included in a solar battery module,for example, a front surface protective sheet, must be highlytransparent to sunlight because the solar battery absorbs sunlight forphotovoltaic power generation, and excellent in properties includingstrength, weather resistance, heat resistance, water resistance, lightresistance, wind endurance, hail storm resistance and chemicalresistance. Particularly, the protective sheet must be excellent inmoisture-proof property to prevent the permeation of moisture andoxygen, have a high surface hardness, excellent in soil resistance toprevent dust accumulation, have very high durability and protectiveability. The back protective sheet must meet substantially the sameconditions as those for the front surface protective sheet.

[0008] The glass sheet, which is the most commonly used at present asthe front surface protective sheet of the solar battery module, has ahigh sunlight transmittance, is excellent in properties relating todurability, such as weather resistance, heat resistance, waterresistance, light resistance and chemical resistance, is excellent inmoistureproof property, has a high surface hardness, is excellent insoil resistance to prevent dust accumulation and has high protectiveability. However, the glass sheet is inferior in strength, plasticity,impact resistance, workability, handling facility and cost.

[0009] Although the fluorocarbon resin sheet serving as the frontsurface protective sheet of the solar battery module, as compared withthe glass sheet, is satisfactory in strength, plasticity, impactresistance and weight, the same is inferior in properties relating todurability including weather resistance, heat resistance, waterresistance light resistance and chemical resistance, and is particularlyunsatisfactory in moistureproof property and soil resistance.

[0010] Although a resin sheet having a high strength, as employed as theback protective sheet of the solar battery module, is satisfactory instrength, plasticity, impact resistance, weight and cost, the same isinferior in properties relating to durability including weatherresistance, heat resistance, water resistance, light resistance andchemical resistance and, particularly, lacks moistureproof property andsoil resistance.

[0011] There have been a proposal to use sheets of a material having anexcellent gas-barrier property and impermeable to moisture, oxygen gasand the like as the front or the back surface protective sheet of thesolar battery module. The most commonly used sheets having an excellentgas-barrier property are aluminum foils.

[0012] Although very excellent in gas-barrier property, aluminum foilscause problems in the disposal thereof and, basically, aluminum foilsare opaque and obstruct the view of things behind them.

[0013] A resin film excellent in gas-barrier property, such as a film ofa polyvinylidene chloride resin, or a polyvinyl alcohol resin or anethylene-vinyl alcohol copolymer is a previously proposed resin filmexcellent in gas-barrier property. The resin film of a polyvinylidenechloride resin produces chlorinated gases when incinerated. Therefore,it is undesirable to use such a film in view of preventing environmentalpollution. Basically, the gas-barrier property of that resin film is notnecessarily satisfactory and that resin film is unsuitable for usesrequiring a high gas-barrier property. The resin film of the polyvinylalcohol resin or the ethylene-vinyl alcohol copolymer has a relativelyexcellent gas-barrier property in an absolute dry condition and is notsatisfactory in impermeability to moisture. The impermeability of thisresin film to oxygen gas deteriorates under a moist condition.Accordingly, this film is unsuitable, from the practical point of view,for use as a gas-barrier film.

[0014] A recently proposed gas-barrier film excellent in gas-barrierproperty is, for example, an inorganic oxide film, such as a siliconoxide film or an aluminum oxide film, deposited by a physical vapordeposition process, such as a vacuum evaporation process, or a chemicalvapor deposition process, such as a low-temperature plasma chemicalvapor deposition process.

[0015] The gas-barrier film formed by depositing such an inorganic oxideis an aggregate of inorganic oxide grains and inevitably has defects inits structure, which limits reliability in gas-barrier property. Sincesuch a gas-barrier film has a glassy structure, the gas-barrier film isinferior in flexibility and is subject to cracking when mechanicalstress is induced therein. When cracked, the gas-barrier property of thegas-barrier film deteriorates greatly.

[0016] A previously proposed composite gas-barrier film is a multilayergas-barrier film comprising a plurality of component films formed by amultistage vapor deposition process. Another previously proposedcomposite gas-barrier film comprises a resin film having an excellentgas-barrier property and a deposited inorganic oxide film deposited onthe surface of the resin film. These composite gas-barrier films are notnecessarily satisfactory.

DISCLOSURE OF THE INVENTION

[0017] The present invention provides a safe protective sheet for asolar battery module, having a high strength, excellent in propertiesincluding weather resistance, heat resistance, water resistance, lightresistance, wind endurance, hailstorm resistance, chemical resistance,moisture resistance and soil resistance, greatly improved inmoistureproof property to prevent the permeation of moisture and oxygen,capable of limiting long-term deterioration to the least extent, havingvery high durability and protective ability, and capable of beingmanufactured at a low cost; a method of fabricating the protectivesheet; and a solar battery module.

[0018] The present invention provides a protective sheet for a solarbattery module, comprising a weather-resistant sheet and an inorganicoxide thin film deposited on one surface of the weather-resistant sheetby vapor deposition.

[0019] The present invention provides a protective sheet for a solarbattery module, formed by superposing a pair of laminated sheet eachcomprising a weather-resistant sheet and an inorganic oxide thin filmdeposited by vapor deposition.

[0020] The present invention provides a protective sheet for a solarbattery module, comprising a weather-resistant sheet and an ultravioletray intercepting layer, an infrared ray intercepting layer or a highlyreflecting layer.

[0021] The present invention provides a method of fabricating aprotective sheet of a laminated construction comprising at least aweather-resistant sheet and an ultraviolet ray intercepting layer formedon the weather-resistant sheet for a solar battery module, comprisingthe steps of: preparing the weather-resistant sheet; and forming theultraviolet ray intercepting layer by applying a coating resin liquidcontaining TiO₂ or CeO₂ having a mean grain size in the range of 1 to100 nm dispersed therein to the weather-resistant sheet and drying thesame.

[0022] The present invention provides a method of fabricating aprotective sheet of a laminated construction comprising at least aweather-resistant sheet and an infrared ray intercepting layer formed onthe weather-resistant sheet for a solar battery module, comprising thesteps of: preparing the weather-resistant sheet; and forming theinfrared ray intercepting layer y depositing a metal on theweather-resistant sheet by vapor deposition or by applying a coatingresin liquid containing a metal oxide particles dispersed therein to theweather-resistant sheet and drying the same.

[0023] The present invention provides a solar battery module comprising:solar cells; a pair of filler layers sandwiching the solar cellstherebetween; and a pair of protective sheet disposed on the fillerlayers, respectively; wherein at least one of the protective sheetcomprises a weather-resistant sheet and an inorganic oxide thin filmformed by vapor deposition.

[0024] The present invention provides a solar battery module comprising:solar cells; a pair of filler layers sandwiching the solar cellstherebetween; and a pair of protective sheet disposed on the fillerlayers, respectively; wherein at least one of the protective sheet isformed by superposing a pair of laminated structures each comprising aweather-resistant sheet and an inorganic oxide thin film formed by vapordeposition.

[0025] The present invention provides a solar battery module comprising:solar cells; a pair of filler layers sandwiching the solar cellstherebetween; and a pair of protective sheet disposed on the fillerlayers, respectively; wherein at least one of the protective sheetcomprises a weather-resistant sheet, and an ultraviolet ray interceptinglayer, an infrared ray intercepting layer or a highly reflective layerformed on one of the surfaces of the weather-resistant sheet.

[0026] The present invention provides a solar battery module comprising:solar cells; a pair of filler layers sandwiching the solar cellstherebetween; and a pair of protective sheet disposed on the fillerlayers, respectively; wherein at least one of the protective sheetcomprises a weather-resistant sheet and a light confining layer formedon one of the surfaces of the weather-resistant sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a typical sectional view of a protective sheet in afirst embodiment according to the present invention for a solar batterymodule;

[0028]FIG. 2 is a typical sectional view of a protective sheet for asolar battery module;

[0029]FIG. 3 is a typical sectional view of a protective sheet for asolar battery module;

[0030]FIG. 4 is a typical sectional view of a protective sheet for asolar battery module;

[0031]FIG. 5 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 1;

[0032]FIG. 6 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 1;

[0033]FIG. 7 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 1;

[0034]FIG. 8 is a diagrammatic view of a continuous vapor depositionsystem for forming an inorganic oxide thin film by a physical vapordeposition process for vapor deposition

[0035]FIG. 9 is a diagrammatic view of a low-temperature plasma chemicalvapor deposition system for forming an inorganic oxide thin film by aphysical vapor deposition process for vapor deposition;

[0036]FIG. 10 is a typical sectional view of a protective sheet in athird embodiment according to the present invention for a solar batterymodule;

[0037]FIG. 11 is a typical sectional view of a protective sheet for asolar battery module;

[0038]FIG. 12 is a typical sectional view of a protective sheet for asolar battery module;

[0039]FIG. 13 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 10;

[0040]FIG. 14 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 10;

[0041]FIG. 15 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 10;

[0042]FIG. 16 is a typical sectional view of a protective sheet in afourth embodiment according to the present invention for a solar batterymodule;

[0043]FIG. 17 is a typical sectional view of a protective sheet for asolar battery module;

[0044]FIG. 18 is a typical sectional view of a protective sheet for asolar battery module;

[0045]FIG. 19 is a typical sectional view of a protective sheet for asolar battery module;

[0046]FIG. 20 is a typical sectional view of a protective sheet for asolar battery module;

[0047]FIG. 21 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 16;

[0048]FIG. 22 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 16;

[0049]FIG. 23 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 16;

[0050]FIG. 24 is a typical sectional view of a protective sheet in afifth embodiment according to the present invention for a solar batterymodule;

[0051]FIG. 25 is a typical sectional view of a protective sheet for asolar battery module;

[0052]FIG. 26 is a typical sectional view of a protective sheet for asolar battery module;

[0053]FIG. 27 is a typical sectional view of a protective sheet for asolar battery module;

[0054]FIG. 28 is a typical sectional view of a protective sheet for asolar battery module;

[0055]FIG. 29 is a typical sectional view of a solar battery moduleprovided with the protective sheet shown in FIG. 24;

[0056]FIG. 30 is a typical sectional view of a protective sheet inExample 1 in a seventh embodiment according to the present invention fora solar battery module;

[0057]FIG. 31 is a typical sectional view of a protective sheet inExample 2 in a seventh embodiment according to the present invention fora solar battery module;

[0058]FIG. 32 is a typical sectional view of a protective sheet inExample 3 in a seventh embodiment according to the present invention fora solar battery module;

[0059]FIG. 33 is a typical sectional view of a protective sheet inExample 4 in a seventh embodiment according to the present invention fora solar battery module;

[0060]FIG. 34 is a typical sectional view of a solar battery moduleembodying the present invention;

[0061] FIGS. 35(a) to 35(e) are typical sectional views of assistance inexplaining a process of fabricating a protective sheet in an eighthembodiment according to the present invention for a solar batterymodule;

[0062] FIGS. 36(a) to 36(e) are typical sectional views of assistance inexplaining a process of fabricating a protective sheet in a modificationof the protective sheet shown in FIG. 35;

[0063] FIGS. 37(a) and 37(b) are typical sectional views of a lightconfining layer included in a protective sheet for a solar batterymodule;

[0064] FIGS. 38(a), 38(b) and 38(c) are a typical plan view, a typicalsectional view and a typical perspective view, respectively, of anexample of a reflecting structure included in the light confining layershown in FIGS. 37(a) and 37(b);

[0065] FIGS. 39(a), 39(b) and 39(c) are a typical plan view, a typicalsectional view and a typical perspective view, respectively, of anotherexample of a reflecting structure included in the light confiningstructure; and

[0066]FIG. 40 is a typical sectional view of a solar battery moduleembodying the present invention provided with a protective sheet.

BEST MODE FOR CARRYING OUT THE INVENTION

[0067] First Embodiment

[0068] The present invention will be described hereinafter withreference to the accompanying drawings.

[0069] In this description, the term “sheet” is used in its broad senseto denote both sheets and films, and the term “film” is used in itsbroad sense to denote both sheets and films.

[0070] FIGS. 1 to 4 are typical sectional views of protective sheets inexamples in a first embodiment according to the present invention for asolar battery module, and FIGS. 5 to 6 are typical sectional views ofsolar battery modules employing the protective sheet shown in FIG. 1.

[0071] Referring to FIG. 1, a protective sheet A embodying the presentinvention for a solar battery module comprises a fluorocarbon resinsheet (weather-resistant sheet) 1, and a deposited inorganic oxide thinfilm 2 formed on one of the surfaces of the fluorocarbon resin sheet 1.

[0072] As shown in FIG. 2, a protective sheet A₁ in an example of thefirst embodiment for a solar battery module is formed bysurface-treating one of the surfaces of a fluorocarbon resin sheet 1 toform a surface-treated layer 3, and forming a deposited inorganic oxidethin film 2 on the surface-treated layer 3 of the fluorocarbon resinsheet 1.

[0073] As shown in FIG. 3, a protective sheet A₂ in another example ofthe first embodiment for a solar battery module is formed by forming amultilayer film 4 consisting of at least two deposited inorganic oxidethin films 2 on one of the surfaces of a fluorocarbon resin sheet 1.

[0074] As shown in FIG. 4 a protective sheet A₃ in a third example ofthe first embodiment for a solar battery module comprises a fluorocarbonresin sheet 1 and a composite film 5 formed on one of the surfaces ofthe fluorocarbon resin film 1. The composite film 5 consists of a firstdeposited inorganic oxide thin film 2 a formed on one of the surfaces ofthe fluorocarbon resin sheet 1 by a chemical vapor deposition process,and a second deposited inorganic oxide thin film 2 b of an inorganicoxide different from that of the first deposited inorganic oxide film 2a, formed on the first deposited inorganic oxide thin film 2 a by aphysical vapor deposition process.

[0075] Those protective sheets are only examples of the protective sheetin the first embodiment and the present invention is not limitedthereto.

[0076] For example, in each of the protective sheets shown in FIGS. 3and 4, the surface of the fluorocarbon resin sheet 1 may be finished ina surface-treated surface similar to the surface-treated surface 3 shownin FIG. 2. In the protective sheet A₃ shown in FIG. 4, a depositedinorganic oxide thin film may be formed first on the surface of thefluorocarbon resin sheet 1 by a physical vapor deposition process, andthen another deposited inorganic oxide thin film may be formed by achemical vapor deposition process.

[0077] A solar battery module employing this protective sheet Aembodying the present invention and shown in FIG. 1 will be described byway of example. Referring to FIG. 5, a solar battery module T employsthe protective sheet A shown in FIG. 1 as its front surface protectivesheet 11. The solar battery module T is fabricated by super posing theprotective sheet 11(A), a filler layer 12, a photovoltaic layer 13 ofsolar cells, a filler layer 14 and a generally known back surfaceprotective sheet 15 in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The deposited inorganic oxide thinfilm 2 of the protective sheet 11 faces inside.

[0078] Another solar battery module T₁ shown in FIG. 6 employs theprotective sheet A shown in FIG. 1 as its back surface protective sheet16. The solar battery module T₁ is fabricated by superposing a generallyknown front surface protective sheet 17, a filler layer 12, aphotovoltaic layer 13 of solar cells, a filler layer 14 and theprotective sheet 16(A) in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The deposited inorganic oxide thinfilm 2 of the protective sheet 16 faces inside.

[0079] A third solar battery module T₂ shown in FIG. 7 employs theprotective sheet A shown in FIG. 1 as its front surface protective sheet11 and its back surface protective sheet 16. The solar battery module T₂is fabricated by superposing the front surface protective sheet 11(A), afiller layer 12, a photovoltaic layer 13 of solar cells, a filler layer14 and the protective sheet 16(A) in that order in a superposedstructure, and subjecting the superposed structure to a generally knownforming process, such as a lamination process, in which those componentlayers of the superposed structure are brought into close contact byvacuum and are bonded together by hot pressing. The deposited inorganicoxide thin film 2 of each of the protective sheets 11 and 16 facesinside.

[0080] The foregoing protective sheets in accordance with the presentinvention and the foregoing solar battery modules employing thoseprotective sheets are examples intended to illustrate the invention andnot to be construed to limit the scope of the invention.

[0081] For example, the protective sheets shown in FIGS. 2, 3 and 4 canbe applied to solar battery modules of various types. The foregoingsolar battery modules may comprise additional layers for sunlightabsorption, reinforcement or the like.

[0082] Materials for and methods of fabricating the protective sheets inaccordance with the present invention and the solar battery modulesemploying those protective sheets will be described. The fluorocarbonresin sheet 1 for the protective sheets embodying the present inventionand the solar battery modules employing those protective sheets is atransparent film or a transparent sheet of any one ofpolytetrafluoroethylene (PTFE), perfluoroalcoxy resins (PFA), i.e.,copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether,tetafluoroethylene-hexafluoropropylene copolymers (FEP),tetrafluoroethylene-perfluoroalkyl vinyl ether-hexafluoro-propylenecopolymers (EPE), tetrafluoroethylene-ethylene or propylenecopolymers(ETFE), polychlorotrifluoroethyleneresins (PCTFE),ethylene-chlorotrifluoroethylene copolymers (ECTFE), vinylidene fluorideresins (PVDF), and polyvinyl fluorides (PVF).

[0083] Sheets of polyvinyl fluorides (PVF) andtetrafluoro-ethylene-ethylene or -propylene copolymers (ETFE) among theforegoing fluorocarbon resin sheets 1 are most preferable from theviewpoint of transparency and transmittance to sunlight.

[0084] The protective sheets of the solar battery modules using thefluorocarbon resin sheet 1 utilize the excellent properties of thefluorocarbon resin sheet 1 including mechanical properties, heatresistance, optical properties, weather resistance including lightresistance, heat resistance, water resistance and the like, soilresistance and chemical resistance. The protective sheet is equal inoptical properties and durability to a glass sheet generally used as aprotective sheet, has satisfactory mechanical properties, and is moreflexible and lighter than a glass sheet, excellent in workability andeasy to handle.

[0085] The fluorocarbon resin sheet 1 may be, for example, any one offilms or sheets of the foregoing fluorocarbon resins formed by a filmforming process, such as an extrusion process, a casting process, aT-die extrusion process, a cutting process, an inflation process or thelike, any one of multilayer films or multilayer sheets of two or morekinds of the foregoing fluorocarbon resins formed by a coextrusionprocess, or any one of films or sheets formed by subjecting a mixture ofa plurality of kinds of the foregoing fluorocarbon resins to a filmforming process. When necessary, the fluorocarbon resin sheet 1 may be auniaxially or biaxially oriented film or sheet formed by subjecting afluorocarbon resin film or sheet to a uniaxial or biaxial orientationprocess of a tenter system or a tubular film system.

[0086] The thickness of the fluorocarbon resin sheet is in the range ofabout 12 to about 200 μm, desirably, in the range of about 25 to about150 μm.

[0087] It is desirable that the fluorocarbon resin sheet 11 of thepresent invention has a visible light transmittance of 90% or above,preferably, 95% or above and a property to transmit all incidentsunlight and to absorb the same.

[0088] When forming the fluorocarbon resin sheet, various compoundingingredients and additives may be added to the fluorocarbon resin toimprove the workability, heat resistance, weather resistance, mechanicalproperties, dimensional stability, oxidation resistance, slipperiness,releasability, flame retardancy, antifungal property, electricproperties and the like. The amount of each of the compoundingingredients and the additives is in the range of a very small percent toseveral tens percent and may optionally be determined according to thepurpose.

[0089] The fluorocarbon resin may contain commonly known additives, suchas a lubricant, a crosslinking agent, an oxidation inhibitor, anultraviolet absorber, a light stabilizer, a filler, a reinforcingmaterial, a stiffener, an antistatic agent, a flame retarder, aflame-resistant agent, a foaming agent, an antifungus agent, a pigmentand the like. The fluorocarbon resin may further contain modifiers.

[0090] In the present invention, it is preferable to use a fluorocarbonresin sheet of a fluorocarbon resin produced by preparing a mixture of afluorocarbon resin, and an oxidation inhibitor or an ultravioletabsorber, and kneading the mixture.

[0091] In the present invention, it is preferable to use a fluorocarbonresin sheet of a fluorocarbon resin produced by preparing a mixture of afluorocarbon resin, an oxidation inhibitor and/or an ultravioletabsorber, and kneading the mixture.

[0092] The ultraviolet absorber absorbs detrimental ultraviolet rayscontained in sunlight, converts the energy of ultraviolet rays intoharmless thermal energy in its molecules to prevent active species thatstarts the photo deterioration of polymers from being excited. One orsome of ultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

[0093] The oxidation inhibitor prevents the light deterioration orthermal deterioration of polymers. Suitable oxidation inhibitors are,for example, those of a phenol group, an amine group, a sulfur group, aphosphoric acid group and the like.

[0094] The ultraviolet absorber or the oxidation inhibitor may be anultraviolet absorbing polymer or an oxidation inhibiting polymerproduced by chemically bonding an ultraviolet absorber of thebenzophenone group or an oxidation inhibitor of the phenol group to theprincipal chains or the side chains of a polymer.

[0095] The ultraviolet absorber and/or the oxidation inhibitor contentis dependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

[0096] When necessary, a surface-treated layer 3 may be formed in asurface of the fluorocarbon resin sheet 1 by a surface pretreatmentprocess to improve the adhesion between the surface of the fluorocarbonresin sheet 11 and the deposited inorganic oxide thin film 2.

[0097] The surface-treated layer 3 may be formed by, for example, acorona discharge treatment, an ozone treatment, a low-temperature plasmatreatment using oxygen gas or nitrogen gas, a glow discharge treatment,an oxidation treatment using a chemical or the like. The surface-treatedlayer 3 may be a corona-treated layer, an ozone-treated layer, aplasma-treated layer, an oxidized layer or the like.

[0098] The surface pretreatment of the fluorocarbon resin sheet may becarried out before forming the deposited inorganic oxide thin film. Whenthe surface of the fluorocarbon resin sheet is to be treated by alow-temperature plasma process or a glow discharge process, the surfacepretreatment may be carried out in an in-line processing mode as apretreatment process in a process for forming the deposited inorganicoxide thin film, which is effective in reducing the manufacturing cost.

[0099] The surface of the fluorocarbon resin sheet 1 is finished by thesurface pretreatment to improve the adhesion between the fluorocarbonresin sheet 1 and the deposited inorganic oxide thin film 2. Theimprovement of adhesion can be achieved by forming, instead of formingthe surface-treated layer, a layer of a primer, an undercoater, ananchoring agent, an adhesive or a deposited undercoating material.

[0100] Suitable materials for forming the coating layer are, forexample, composite resins containing a polyester resin, a polyamideresin, a polyurethane resin, an epoxy resin, a phenolic resin, a(meta)acrylic resin, a polyvinyl acetate resin, a polyolefin resin suchas a polyethylene, a polypropylene or a copolymer or a resin obtained bymodifying one of those resins, a cellulose resin or the like as aprincipal component of a vehicle.

[0101] In the present invention, the composite resin may contain anultraviolet absorber and/or an oxidation inhibitor for light resistanceimprovement.

[0102] The ultraviolet absorber absorbs detrimental ultraviolet rays insunlight, converts the energy of ultraviolet rays into harmless thermalenergy in its molecules to prevent active species that starts thephotodeterioration of polymers from being excited. One or some ofultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

[0103] The oxidation inhibitor prevents the light deterioration orthermal deterioration of polymers. Suitable oxidation inhibitors are,for example, those of a phenol group, an amine group, a sulfur group, aphosphoric acid group and the like.

[0104] The ultraviolet absorber or the oxidation inhibitor may be anultraviolet absorbing polymer or an oxidation inhibiting polymerproduced by chemically bonding an ultraviolet absorber of thebenzophenone group or an oxidation inhibitor of the phenol group to theprincipal chains or the side chains of a polymer.

[0105] The ultraviolet absorber and/or the oxidation inhibitor contentis dependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

[0106] The coating layer may be formed of a coating material of, forexample, a solvent type, an aqueous type or an emulsion type by a rollercoating process, a gravure coating process, a kiss-roll coating processor the like. The coating layer may be formed by a coating processsubsequent to a fluorocarbon resin sheet forming process or a biaxialorientation process, or by an in-line coating process included in thefilm forming process or the biaxial orientation process.

[0107] The surface-treated layer 3 may be formed on one surface of thefluorocarbon resin sheet to protect the fluorocarbon resin sheet fromvapor deposition conditions for forming the deposited inorganic oxidethin film, to suppress yellowing, deterioration, shrinkage or cohesivefailure in a surface layer or an inner layer of the fluorocarbon resinsheet, and to improve the adhesion between the fluorocarbon resin sheetand the deposited inorganic oxide thin film. The surface-treated layer3, i.e., a deposition-resistant protective film, such as a depositedinorganic oxide thin film, may be formed by, for example, a chemicalvapor deposition process (CVD process), such as a plasma chemical vapordeposition process, a thermal chemical vapor deposition process or aphotochemical vapor deposition process, or a physical vapor depositionprocess (PVD process), such as a vacuum evaporation process, asputtering process or an ion plating process.

[0108] The thickness of the deposition-resistant protective film ofsilicon oxide or the like may be less than 150 Å. Thedeposition-resistant protective film may be a nonbarrier film not havingany barrier effect to inhibit the permeation of source gases and oxygengas. Concretely, the thickness of the deposition-resistant protectivefilm is in the range of about 10 to about 100 Å, preferably, in therange of about 20 to 80 Å, more preferably, in the range of about 30 toabout 60 Å.

[0109] If the thickness is greater than 150 Å, more concretely 100 Å, 80Å or 60 Å, the fluorocarbon resin sheet is exposed to severe depositionconditions. Consequently, the fluorocarbon resin sheet turns yellow,cohesive failure occurs, the formation of a satisfactorydeposition-resistant protective film becomes difficult, and cracksdevelop in the film. If the thickness is less than 10 Å, 20 Å or 30 Å,the film is incapable of functioning as an effectivedeposition-resistant protective film.

[0110] The protective sheet of the present invention for a solar batterymodule, and the deposited inorganic oxide thin film 2 included in thesolar battery module will be described. The deposited inorganic oxidethin film may be a single-layer deposited inorganic oxide thin film, amultilayer film consisting of a plurality of deposited thin films of aninorganic oxide, or a composite film consisting of a plurality ofdeposited thin films respectively formed of different inorganic oxidesby a physical vapor deposition process, a chemical vapor depositionprocess, or both a physical vapor deposition process and a chemicalvapor deposition process.

[0111] The deposited inorganic oxide thin film formed by a physicalvapor deposition process will be described. The physical vapordeposition process (PVD process) for forming the deposited inorganicoxide thin film may be, for example, a vacuum evaporation process, asputtering process or anion plating process.

[0112] A deposited film can be deposited on a fluorocarbon resin sheetby a vacuum evaporation process using a metal oxide as a sourcematerial, an oxidation vapor deposition process using a metal or a metaloxide, performing oxidation and depositing a metal oxide on thefluorocarbon resin sheet or a plasma-assisted oxidation vapor depositionprocess carrying out a plasma-assisted oxidation.

[0113] In the foregoing process, the evaporation material may be heatedby, for example, a resistance heating method, a radio frequency heatingmethod or an electron beam (EB) heating method.

[0114]FIG. 8 is a diagrammatic view of a continuous vacuum evaporationsystem for forming the deposited inorganic oxide thin film by a physicalvapor deposition process.

[0115] Referring to FIG. 8, in a continuous vacuum evaporation system21, a fluorocarbon resin sheet 1 unwound from a feed roll 23 disposed ina vacuum chamber 22 is guided to a cooling coating drum 26 by guiderollers 24 and 25.

[0116] A source material 28, such as aluminum or aluminum oxide,contained in a crucible 27 is heated and vaporized, and the vaporizedsource material 28 is deposited on the fluorocarbon 41 resin sheet 1wound around the cooling coating drum 26. When necessary, oxygen gas isblown through an oxygen gas supply opening 29 into the vacuum chamber22. The evaporated source material 28 is deposited through masks 30 onthe fluorocarbon resin sheet 1 in a deposited inorganic oxide thin film,such as an aluminum oxide deposited thin film. The fluorocarbon resinsheet 1 coated with the deposited inorganic oxide thin film, such as analuminum oxide deposited thin film, is guided through guide rollers 25′and 24′ and is taken up in a take-up roll 31. A multilayer depositedinorganic oxide thin film consisting of a plurality of inorganic oxidefilms can be formed on a fluorocarbon resin sheet by forming a firstdeposited inorganic oxide thin film on a fluorocarbon resin sheet by afirst processing cycle by the continuous vacuum evaporation system, andforming a second deposited inorganic oxide thin film on the firstdeposited inorganic oxide thin film by a second processing cycle by thesame continuous vacuum evaporation system. It is also possible to formthe multilayer deposited inorganic oxide thin film consisting of aplurality of deposited inorganic oxide thin films by successivelyprocessing the fluorocarbon resin sheet by a plurality of continuousvacuum evaporation systems similar to the foregoing continuous vacuumevaporation system.

[0117] Basically, the deposited inorganic oxide thin film may be adeposited thin film of a metal oxide, such as the oxide of silicon (Si),aluminum (Al), magnesium (Mg), Calcium (Ca), potassium (K), tin (Sn),sodium (Na), boron (B), titanium (Ti), lead (Pb), zirconium (Zr),yttrium (Y) or the like.

[0118] Preferable metal oxide deposited thin films are those of oxidesof silicon (Si) and aluminum (Al).

[0119] The metal oxide deposited thin film can referred to as metaloxide, such as silicon oxide, aluminum oxide and magnesium oxide. Thosemetal oxides are represented by MO_(x) (SiO_(x), AlO_(x), MgO_(x)),where “x” is dependent on the valence of the metal.

[0120] The values of “x” re 0 to 2 for silicon (Si), 0 to 1.5 foraluminum (Al), 0 to 1 for magnesium (Mg), 0 to 1 for calcium (Ca), 0 to0.5 for potassium (K), 0 to 2 for tin (Sn), 0 to 0.5 for sodium (Na), 0to 1.5 for boron (B), 0 to 2 for titanium (Ti), 0 to 2 for lead (Pb), 0to 2 for zirconium (Zr) and 0 to 1.5 for yttrium (Y).

[0121] When x=0, the material is a metal, the film of the material isnot transparent and hence cannot be used. When the value of “x” is amaximum, the material is a complete oxide of the metal.

[0122] Although dependent on the kind of the metal or the metal oxide,the thickness of the inorganic oxide thin film is, for example, in therange of about 50 to about 2000 Å, preferably, about 100 to about 1000Å. A mixture of different metals or a mixture of different metal oxidesmay be used for forming the deposited inorganic oxide thin film. Thedeposited inorganic oxide thin film may be a film of a mixture ofdifferent inorganic oxides.

[0123] Further description will be given of the formation of thedeposited inorganic oxide thin film by a chemical vapor depositionprocess. The deposited inorganic oxide thin film can be formed by achemical vapor deposition process, such as a plasma chemical vapordeposition process, a thermal chemical vapor deposition process or aphotochemical vapor deposition process.

[0124] More concretely, a deposited thin film of an inorganic oxide,such as silicon oxide can be formed by a low-temperature plasma chemicalvapor deposition process using an evaporation monomer gas, such as anorganic silicon compound gas, as a source gas, an inert gas, such asargon gas or helium gas, as a carrier gas and oxygen gas as an oxygensupply gas. The low-temperature plasma chemical vapor deposition processis carried out by a low-temperature plasma chemical vapor depositionsystem. The low-temperature plasma chemical vapor deposition system mayuse, for example, a radio frequency plasma producing system, apulse-wave plasma producing system or a microwave plasma producingsystem. It is desirable to use a radio frequency plasma producing systemto produce a highly active, stable plasma.

[0125] A low-temperature plasma chemical vapor deposition process forforming the deposited inorganic oxide thin film will concretely bedescribed by way of example. FIG. 9 is a diagrammatic view of alow-temperature plasma chemical vapor deposition system for carrying outthe low-temperature plasma chemical vapor deposition process for formingthe deposited inorganic oxide thin film.

[0126] Referring to FIG. 9, in a low-temperature plasma chemical vapordeposition system 41, a fluorocarbon resin sheet 1 unwound from a feedroll 43 disposed in a vacuum chamber 42 is guided to the circumferenceof a cooling electrode drum 45 by guide roller 44 at a predeterminedmoving speed.

[0127] Oxygen gas, an inert gas, a deposition monomer gas, such as anorganic silicon compound gas, and such are supplied from gas supplyunits 46 and 47 and a source material volatilizing unit 48. Thecomposition of a mixed gas consisting of oxygen gas, the inert gas, thedeposition monomer gas and such is adjusted. The mixed gas of apredetermined composition is supplied through a gas supply nozzle 49into the vacuum chamber 42. A plasma 50 is produced on the fluorocarbonresin sheet 1 wound round the cooling electrode drum 45 by glowdischarge to deposit a deposited thin film of an organic oxide, such assilicon oxide, on the fluorocarbon resin sheet 1.

[0128] Predetermined power is supplied to the cooling electrode drum 45by a power supply 51 disposed outside the vacuum chamber 42. A magnet 52is disposed near the cooling electrode drum 45 to promote the productionof the plasma. The fluorocarbon resin sheet 1 provided with thedeposited thin film of the inorganic oxide, such as silicon oxide, isguided to a take-up roll 54 by a guide roller 53 and is taken up on thetake-up roll 54. Thus, the deposited inorganic oxide thin film can beformed by the plasma chemical vapor deposition process. In FIG. 9,indicated at 55 is a vacuum pump.

[0129] The foregoing protective sheet and the foregoing method offabricating the same are only examples and are not to be construed tolimit the scope of the present invention.

[0130] The deposited inorganic oxide thin film is not limited to asingle-layer deposited inorganic oxide thin film but may be a multilayerfilm consisting of a plurality of deposited thin films of an inorganicoxide, or a composite film consisting of a plurality of deposited thinfilms respectively formed of different inorganic oxides.

[0131] According to the present invention, a multilayer depositedinorganic oxide thin film consisting of a plurality of inorganic oxidefilms can be formed on a fluorocarbon resin sheet by forming a firstdeposited inorganic oxide thin film on a fluorocarbon resin sheet by afirst processing cycle by the low-temperature plasma chemical vapordeposition system , and forming a second deposited inorganic oxide thinfilm on the first deposited inorganic oxide thin film by a secondprocessing cycle by the same low-temperature plasma chemical vapordeposition system. It is also possible to form the multilayer depositedinorganic oxide thin film consisting of a plurality of depositedinorganic oxide thin films by successively processing the fluorocarbonresin sheet by a plurality of low-temperature plasma chemical vapordeposition systems similar to the foregoing low-temperature plasmachemical vapor deposition system.

[0132] Monomer gases suitable for depositing the deposited thin film ofan inorganic oxide, such as silicon oxide are those of1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, vinyltrimethylsilane, methyl trimethylsilane, hexamethyldisilane,methylsilane, dimethylsilane, trimethylsilane, diethylsilane,propylsilane, phenylsilane, vinyl triethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane,phenyltrimethoxysilane, methyltriethoxysilane,octamethylcyclotetrasiloxane and the like.

[0133] Among the foregoing organic silicon compounds,1,1,3,3-tetramethyldisiloxane or hexamethyldisiloxane is particularlypreferable in view of facility in handling and the characteristics of adeposited thin film formed by using the same as a source gas.

[0134] The inert gas is, for example, argon gas, helium gas or the like.

[0135] A silicon oxide deposited thin film formed by the foregoingprocess according to the present invention is a reaction productproduced through the interaction of the monomer gas of an inorganicsilicon compound or the like and oxygen gas and firmly adhering to thefluorocarbon resin sheet and is dense and highly flexible. The siliconoxide deposited thin film is a continuous deposited thin film containingsilicon oxide indicated by SiO_(x) (x=0 to 2) as a principal component.

[0136] Preferably, the deposited thin film of silicon oxide contains adeposited thin film of silicon oxide indicted by a chemical formulaSiO_(x) (x=1.3 5o 1.9) as a principal component, in view of transparencyand barrier effect.

[0137] The value of x of SiO_(x) is dependent on the mole ratio betweenthe monomer gas and oxygen gas, the energy of the plasma and the like.Generally, the gas permeability is lower, the deposited thin filmbecomes yellowish and the transparency of the deposited thin film islower when the value of x is smaller

[0138] The silicon oxide deposited thin film contains silicon (Si) andoxygen (O) as its essential constituent elements, and contains a verysmall amount of carbon (C), hydrogen (H) or both carbon (C) and hydrogen(H). The thickness of the silicon oxide deposited thin film is in therange of 50 to 500 Å. The content ratio between the essentialconstituent elements and the minor elements varies continuously in adirection along the thickness.

[0139] The foregoing physical properties of the silicon oxide depositedthin film can be determined through the elementary analysis of thesilicon oxide deposited thin film, in which the silicon oxide depositedthin film is analyzed through ion etching in the direction of the depth,by surface analyzer, such as an x-ray photoelectron spectroscope forx-ray photoelectron spectroscopy (XPS) or a secondary ion massspectroscope for secondary ion mass spectroscopy (SIMS).

[0140] Desirably, the thickness of the silicon oxide deposited thin filmis in the range of about 50 to about 2000 Å. More concretely, it isdesirable that the thickness is in the range of about 100 to 1000 Å. Athickness greater than 1000 Å, more specifically, greater than 2000 Å isundesirable, because a silicon oxide deposited thin film of such a greatthickness is liable to crack. A thickness less than 100 Å, morespecifically, less than 50 Å is undesirable, because a silicon oxidedeposited thin film of such a small thickness is incapable offunctioning as a barrier film.

[0141] The thickness can be measured by a fundamental parameter methodusing, for example, a fluorescent x-ray spectrometer (RIX2000, availablefrom K. K. Rigaku).

[0142] The thickness of the silicon oxide deposited thin film can bechanged by increasing the silicon oxide deposition rate by increasingthe respective flow rates of the monomer gas and oxygen gas or byreducing the deposition rate.

[0143] Each of the component deposited inorganic oxide thin films of theprotective sheet in accordance with the present invention for a solarbattery module, and the solar battery module in accordance with thepresent invention may be a composite film consisting of a plurality ofdeposited thin films of different inorganic oxides formed by using, forexample, both the physical vapor deposition process and the chemicalvapor deposition process in combination.

[0144] It is desirable to form such a composite film consisting of aplurality of deposited thin films of different inorganic oxides by firstdepositing a dense, highly flexible, relatively hard-to-crack inorganicoxide thin film on a fluorocarbon resin sheet by a chemical vapordeposition process, and then depositing a deposited inorganic oxide thinfilm on the previously formed deposited inorganic oxide thin film by aphysical vapor deposition process.

[0145] Naturally, such a composite film consisting of a plurality ofdeposited thin films may be formed by first depositing an inorganicoxide thin film on a fluorocarbon resin sheet by a physical vapordeposition process, and then depositing a dense, highly flexible,relatively hard-to-crack inorganic oxide thin film on the previouslydeposited inorganic oxide thin film by a chemical vapor depositionprocess.

[0146] An ordinary front surface protective sheet included in a solarbattery module will be described. The front surface protective sheetmust be highly transparent to sunlight and insulating, must besatisfactory in properties including weather-resistant propertiesincluding heat resistance, light resistance and water resistance, windendurance, hailstorm resistance, chemical resistance, moisture-proofproperty and soil resistance, must be excellent in physical or chemicalstrength and toughness, must be highly durable, and must be excellent inscratch resistance and impact absorbing property for the protection ofsolar cells as photvoltaic cells.

[0147] Glass sheets, and films or sheets of various resins includingfluorocarbon resins, polyamide resins (nylons), polyester resins,polyethylene resins, polypropylene resins, cyclic polyolefin resins,polystyrene resins, polymethyl methacrylate resins, polycarbonateresins, acetal resins and cellulose resins are possible materials forthe protective sheet.

[0148] The films or sheets of those resins may be uniaxially orbiaxially oriented films or sheets.

[0149] The thickness of the films or sheets is in the range of about 12to about 200 μm, preferably, in the range of about 25 to about 150 μm.

[0150] Description will be given of the filler layer 12 underlying thefront surface protective sheet in accordance with the present inventionincluded in the solar battery module. The filler layer 12 must betransparent to transmit and absorb incident sunlight and must beadhesive to the front surface protective sheet. The filler layer 12 mustbe thermoplastic to keep the surfaces of the solar cells, i.e.,photovoltaic cells, flat and smooth and must be excellent in scratchresistance and impact absorbing property to protect the solar cells,i.e., photovoltaic cells.

[0151] Materials suitable for forming the filler layer 12 are, forexample, fluorocarbon resins, ethylene-vinyl acetate copolymers,ionomers, ethylene-acrylic acid or -methacrylic acid copolymers,polyethylene resins, polypropylene resins, acid-modified polyolefinresins produced by modifying polyolefin resins, such as polyethyleneresins or polypropylene resins, by unsaturated carboxylic acid, such asacrylic acid, itaconic acid, maleic acid or fumaric acid, polyvinylbutyral resins, silicone resins, epoxy resins, (meta) acrylic resins,and mixtures of some of those resins.

[0152] The resin forming the filler layer 12 may contain additivesincluding a crosslinking agent, a thermal oxidation inhibitor, a lightstabilizer, an ultraviolet absorber and a photo oxidation inhibitor byan amount that will not affect adversely to the transparency of theresin to improve the weather-resistant properties including heatresistance, light resistance and water resistance.

[0153] From the viewpoint of ensuring weather-resistant propertiesincluding light resistance, heat resistance and water resistance,desirable materials for forming the filler layer on the sunlightreceiving side are fluorocarbon resins and ethylene-vinyl acetateresins.

[0154] The thickness of the filler layer is in the range of about 200 toabout 1000 μm, preferably, in the range of about 350 to about 600 μm.

[0155] The solar cells 13, i.e., photovoltaic cells, of the solarbattery module will be described. The solar cells 13 may be known solarcells, such as crystalline silicon solar cells, polycrystalline siliconsolar cells, amorphous silicon solar cells, copper-indium-selenide solarcells, compound semiconductor solar cells and the like.

[0156] The present invention may employ polycrystalline siliconthin-film solar cells, microcrystalline silicon thin-film solar cells,hybrid solar cells formed by combining crystalline silicon thin-filmsolar cells and amorphous silicon solar cells.

[0157] The filler layer 14 underlying the solar cells of the solarbattery module will be described. The filler layer 14, similarly to thefiller layer 12 underlying the front surface protective sheet, must beadhesive to the back surface protective sheet. The filler layer 14 mustbe thermoplastic to keep the surfaces of the solar cells, i.e.,photovoltaic cells, flat and smooth and must be excellent in scratchresistance and impact absorbing property to protect the solar cells,i.e., photovoltaic cells.

[0158] Differing from the filler layer 12 underlying the front surfaceprotective sheet, the filler layer 14 underlying the solar cells of thesolar battery module need not necessarily be transparent.

[0159] The filler layer 14, similarly to the filler layer 12 underlyingthe front surface protective sheet, may be formed of one of materialsincluding fluorocarbon resins, ethylene-vinyl acetate copolymers,ionomers, ethylene-acrylic acid or -methacrylic acid copolymers,polyethylene resins, polypropylene resins, acid-modified polyolefinresins produced by modifying polyolefin resins, such as polyethyleneresins or polypropylene resins, by unsaturated carboxylic acid, such asacrylic acid, itaconic acid, maleic acid or fumaric acid, polyvinylbutyral resins, silicone resins, epoxy resins, (meta)acrylic resins, andmixtures of some of those resins.

[0160] The resin forming the filler layer 14 may contain additivesincluding a crosslinking agent, a thermal oxidation inhibitor, a lightstabilizer, an ultraviolet absorber and a photo oxidation inhibitor byan amount that will not affect adversely to the transparency of theresin to improve the weather-resistant properties including heatresistance, light resistance and water resistance.

[0161] The thickness of the filler layer is in the range of about 200 toabout 1000 μm, preferably, in the range of about 350 to about 600 μm.

[0162] An ordinary back surface protective sheet included in a solarbattery module will be described. The back surface protective sheet mustbe an insulating resin film or sheet. The back, surface protective sheetmust be satisfactory in weather-resistant properties including heatresistance, light resistance and water resistance, must be excellent inchemical or physical strength and toughness, and must be excellent inscratch resistance and impact absorbing property for the protection ofsolar cells as photvoltaic cells.

[0163] Films or sheets of various resins including polyamide resins(nylons), polyester resins, polyethylene resins, polypropylene resins,cyclic polyolefin resins, polystyrene resins, polycarbonate resins,acetal resins, cellulose resins (meta)acrylic resins and fluorocarbonresins are possible materials for the protective sheet.

[0164] The films or sheets of those resins may be uniaxially orbiaxially oriented films or sheets.

[0165] The thickness of the films or sheets is in the range of about 12to about 200 μm, preferably, in the range of about 25 to about 150 μm.

[0166] The solar battery module of the present invention may be providedwith an additional weather-resistant sheet for the improvement of thestrength, weather resistance, scratch resistance and the durability ofthe solar battery module. Possible materials for forming the additionalweather-resistant sheet are, for example, low-density polyethylenes,medium-density polyethylenes, high-density polyethylenes, linearlow-density polyethylenes, polypropylenes, ethylene-propylenecopolymers, ethylene-vinyl acetate copolymers, ionomers, ethylene-ethylacrylate copolymers, ethylene-acrylate or -methacrylate copolymers,methyl pentene polymers, polybutene resins, polyvinyl chloride resins,polyvinyl acetate resins, polyvinylindene chloride resins, vinylchloride-vinylidene chloride copolymers, poly(meta)acrylic resins,polyacrylonitrile resins, polystyrene resins, acrylonitrile-styrenecopolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABSresins), polyester resins, polyamide resins, polycarbonate resins,polyvinyl alcohol resins, saponified ethylene-vinyl acetate copolymers,fluorocarbon resins, diene resins, polyacetal resins, polyurethaneresins, nitrocellulose, polymers obtained by the polymerization ofcyclopentadiene, cyclopentadiene derivatives, dicyclopentadiene,dicyclopentadiene derivatives, cyclohexadiene, cyclohexadienederivatives, norbornadiene, norbornadiene derivatives and cyclic dienes,transparent cyclic polyolefin resins produced by the copolymerization ofthe cyclic diene, and one or some of olefin monomers including ethylene,propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene and thelike, and other known resins. The additional weather-resistant sheet maybe disposed on the deposited inorganic oxide thin film.

[0167] The films or sheets of those resins may be nonoriented,uniaxially oriented or biaxially oriented.

[0168] There is no restriction on the thickness of those films orsheets; the thickness of the films or sheets may be in the range ofseveral micrometers to about 300 μm.

[0169] The films or sheets may be extruded films, blown films or coatingfilms.

[0170] A method of fabricating the solar battery module in accordancewith the present invention using the foregoing materials will bedescribed hereinafter. The method of fabricating the solar batterymodule uses the protective sheet in accordance with the presentinvention for a solar battery module as the front surface protectivesheet or the back surface protective sheet of the solar battery module.The solar battery module is fabricated by superposing the protectivesheet, the filler layer, a photovoltaic layer of the solar cells, i.e.,photovoltaic cells, the filler layer and a generally known back surfaceprotective sheet in that order in a superposed structure, and subjectingthe superposed structure to a generally known forming process, such as alamination process, in which those component layers of the superposedstructure are brought into close contact by vacuum and are bondedtogether by hot pressing. The deposited inorganic oxide thin film of thefront surface protective sheet faces inside. When necessary, otherlayers are interposed between those component layers.

[0171] When necessary, layers of a hot-melt adhesive, a solventadhesive, a photocurable adhesive or the like containing a (meta)acrylicresin, an olefin resin, a vinyl resin or the like as a principalcomponent of its vehicle may be formed between the component layers toenhance the adhesion between the adjacent component layers.

[0172] When necessary, the contact surfaces of the adjacent componentlayers may be pretreated by a pretreatment process, such as a coronadischarge process, ozonizing process, a low-temperature plasma processusing oxygen gas or nitrogen gas, an atmospheric pressure plasmaprocess, glow discharge process, an oxidation process using a chemicalor the like to enhance the adhesion between the contact surfaces.

[0173] A pretreatment layer of a primer, an undercoating material, anadhesive or an anchoring agent or the like may be formed on the contactsurfaces of the adjacent component layers for a surface pretreatmentprocess.

[0174] The pretreatment layer may be formed of a resin compoundcontaining as a principal component of its vehicle one of resinsincluding, for example, polyester resins, polyamide resins, polyurethaneresins, epoxy resins, phenolic resins, (meta)acrylic resins, polyvinylacetate resins, polyolefin resins, such as polyethylene resins orpolypropylene resins, copolymers or modifications of polyolefin resinsand cellulose resins.

[0175] The coating layer may be formed of a coating material of asolvent type, an aqueous type or an emulsion type by a roll coatingprocess, a gravure coating process, a kiss-roll coating process or thelike.

[0176] The surface pretreatment process may form a deposited inorganicoxide thin film of a thickness in the range of about 20 to about 100 Å,preferably, in the range of about 30 to 60 Å not having barrier effectto improve the adhesion between the adjacent component layers by aprocess similar to the foregoing process for forming the depositedinorganic oxide thin film.

EXAMPLES

[0177] Examples of the first embodiment will be described hereinafter.

Example 1

[0178] (1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet),i.e., base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polyvinyl fluoride sheet was unwound and woundaround a coating drum and a 500 Å thick deposited aluminum oxide thinfilm was deposited on a treated surface of the polyvinyl fluoride sheettreated for adhesion improvement by a reactive vacuum evaporationprocess of an electron beam (EB) heating system. Aluminum was used as anevaporation source and oxygen gas was supplied to the continuous vacuumevaporation system.

[0179] Deposition conditions:

[0180] Evaporation source: Aluminum

[0181] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0182] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0183] EB power: 40 kW

[0184] Sheet moving speed: 600 m/min

[0185] (2) A protective sheet in accordance with the present inventionfor a solar battery module was completed by subjecting the 500 Å thickdeposited aluminum oxide thin film formed on the surface of thepolyvinyl fluoride sheet to a glow-discharge plasma process to form aplasma-processed surface. The glow-discharge plasma process was carriedout by a glow-discharge plasma producing apparatus of 1500 W in plasmaoutput immediately after the deposition of the 500 Å thick depositedaluminum oxide thin film. In the glow-discharge plasma process, anoxygen/argon mixed gas of 19/1 in O₂/Ar ratio was supplied so that thepressure of the oxygen/argon mixed gas is maintained at 6×10⁻⁵ torr andthe processing speed was 420 m/min.

[0186] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated. The protective sheet, a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and a 50 μm thick biaxially oriented polyethylene terephthalatefilm were superposed in that order with the plasma-processed depositedaluminum oxide thin film facing inside and the surface of the 38 μmthick biaxially oriented polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the front surfaceprotective sheet. Those component layers were laminated by usingadhesive layers of an acrylic resin to complete a solar battery module.

[0187] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 2

[0188] (1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film),i.e., base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 500 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polyvinyl fluoride film treatedfor adhesion improvement under the following conditions.

[0189] Deposition conditions:

[0190] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (Unit: slm)

[0191] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0192] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0193] Power supplied to cooling electrode drum: 20 kW

[0194] Film moving speed: 80 m/min

[0195] Surface for vapor deposition: Corona-processed surface

[0196] (2) A protective sheet in accordance with the present inventionfor a solar battery module was completed by subjecting the 500 Å thickdeposited silicon oxide thin film formed on the surface of the polyvinylfluoride film to a corona discharge process to form a corona-processedsurface and to increase the surface tension of the deposited siliconoxide thin film from 35 dyne to 60 dyne. Corona discharge power was 10kW and the sheet was moved at a moving speed of 100 m/min.

[0197] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the corona-processed deposited silicon oxide thinfilm facing inside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0198] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 3

[0199] (1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film)containing an ultraviolet absorber was mounted on a feed roll of aplasma chemical vapor deposition system. A 500 Å thick deposited siliconoxide thin film was deposited on a treated surface of the polyvinylfluoride film treated for adhesion improvement under the followingconditions.

[0200] Deposition conditions:

[0201] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (unit: slm)

[0202] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0203] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0204] Power supplied to cooling electrode drum: 20 kW

[0205] Film moving speed: 80 m/min

[0206] Surface for deposition: Corona-processed surface

[0207] The surface of the 500 Å thick deposited silicon oxide thin filmformed on the polyvinyl fluoride film was subjected to a coronadischarge process to form a corona-processed surface to increase thesurface tension of the deposited silicon oxide thin film from 35 dyne to60 dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

[0208] (2) A roll of the polyvinyl fluoride film provided with thecorona-processed deposited silicon oxide thin film was mounted on a feedroll of a continuous vacuum evaporation system. The polyvinyl fluoridefilm was unwound and wound around a coating drum and a 500 Å thickdeposited aluminum oxide thin film was deposited on the corona-processedsurface of the deposited silicon oxide thin film formed on the polyvinylfluoride film by a reactive vacuum evaporation process of an electronbeam (EB) heating system. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

[0209] Deposition conditions:

[0210] Evaporation source: Aluminum

[0211] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0212] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0213] EB power: 40 kW

[0214] Film moving speed: 600 m/min

[0215] A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 500 Å thickdeposited aluminum oxide thin film formed on the surface of thepolyvinyl fluoride sheet to a glow-discharge plasma process to form aplasma-processed surface. The glow-discharge plasma process was carriedout by a glow-discharge plasma producing apparatus of 1500 W in plasmaoutput immediately after the deposition of the 500 Å thick depositedaluminum oxide thin film. In the glow-discharge plasma process, anoxygen/argon mixed gas of 19/1 in O₂/Ar ratio was supplied so that thepressure of the oxygen/argon mixed gas is maintained at 6×10⁻⁵ torr andthe processing speed was 420 m/min.

[0216] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. Theprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the plasma-processed deposited aluminum oxide thin film facinginside and the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet. Those component layers were laminated byusing adhesive layers of an acrylic resin to complete a solar batterymodule.

[0217] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride film (PVF film).

Example 4

[0218] (1) Protective sheets that are the same as the protective sheetin Example 1 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the solar cells facing the frontsurface protective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0219] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 5

[0220] (1) Protective sheets that are the same as the protective sheetin Example 2 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited silicon oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0221] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 6

[0222] (1) Protective sheets that are the same as the protective sheetin Example 3 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0223] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) containing anultraviolet absorber were used instead of the 50 μm thick polyvinylfluoride sheets (PVF sheet) containing the ultraviolet absorber.

Example 7

[0224] (1) A protective sheet that is the same as the protective sheetin Example 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 3 mm thickglass sheet, and laminating those component layers by using adhesivelayers of an acrylic resin.

[0225] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 8

[0226] (1) A protective sheet that is the same as the protective sheetin Example 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecorona-processed deposited silicon oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

[0227] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 9

[0228] (1) A protective sheet that is the same as the protective sheetin Example 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

[0229] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 10

[0230] (1) A roll of a 50 μm thick fluorocarbon resin sheet of aethylene-tetrafluoroethylene copolymer (ETFE) was mounted on a feed rollof a plasma chemical vapor deposition system. A 50 Å thick depositedsilicon oxide thin film as a surface layer was deposited on a treatedsurface of the fluorocarbon resin sheet treated for adhesion improvementunder the same conditions as those in Example 2.

[0231] Subsequently, a 800 Å thick deposited silicon oxide thin film wasformed on the surface layer by the same process as that in Example 2.The surface of the 800 Å thick deposited silicon oxide thin film wassubjected to the same corona discharge process as in Example 2 toincrease the surface tension of the same from 35 dyne to 60 dyne and toform a protective sheet having a corona-processed surface in accordancewith the present invention for a solar battery module.

[0232] (2) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the corona-processed deposited silicon oxide thinfilm facing inside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the solar cells facing thefront surface protective sheet. Those component layers were laminated byusing adhesive layers of an acrylic resin to complete a solar batterymodule.

[0233] (3) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick polyvinylfluoride sheet (PVF sheet) was used instead of the 50 μm thickfluorocarbon resin sheet of an ethylene-tetrafluoroethylenecopolymer(ETFE).

Example 11

[0234] (1) Protective sheets that are the same as the protective sheetin Example 10 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the corona-processed deposited silicon oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0235] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick polyvinyl fluoride sheets(PVF sheets) were used instead of the 50 μm thick fluorocarbon resinsheets of an ethylene-tetrafluoroethylene copolymer (ETFE).

Comparative Example 1

[0236] A solar battery module was fabricated by superposing a 3 mm thickglass sheet, i.e., base sheet, as a back surface protective sheet, a 400μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and a 50 μm thick biaxially oriented polyethyleneterephthalate film in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick biaxially orientedpolyethylene terephthalate film, and laminating those component layersby using adhesive layers of an acrylic resin.

Comparative Example 2

[0237] A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film in that order with the surfaceof the 38 μm thick polyethylene terephthalate film provided with thearray of amorphous silicon solar cells facing the 50 μm thick polyvinylfluoride sheet, and laminating those component layers by using adhesivelayers of an acrylic resin.

Comparative Example 3

[0238] A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick polyvinyl fluoride sheet (PVF sheet) as a back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin. andlaminating those component layers by using adhesive layers of an acrylicresin.

[0239] Experiments

[0240] The protective sheets in Examples 1 to 11 of the presentinvention and those in Comparative examples 1 to 3 were subjected tototal transmittance measurement. The solar battery modules in Examples 1to 11 and Comparative examples 1 to 3 were subjected to solar batterymodule evaluation tests.

[0241] (1) Total Transmittance Measurement

[0242] Total transmittance (%) of each of the protective sheets inExamples 1 to 11 and Comparative examples 1 to 3 against the totaltransmittance of the base sheet as a reference total transmittance wasmeasured by a color computer.

[0243] (2) Solar Battery Module Evaluation Tests

[0244] The solar battery modules were subjected to environmental testsin conformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

[0245] (3) Moisture Permeability and Oxygen Permeability

[0246] The moisture permeabilities of the protective sheets in Examples1 to 11 and Comparative examples 1 to 3 were measured in an atmosphereof 40° C. and 90% RH by a moisture permeability measuring apparatus(PERMATRAN, MOCON, USA). The oxygen permeabilities of the protectivesheets in Examples 1 to 11 and Comparative examples 1 to 3 were measuredin an atmosphere of 23° C. and 90% RH by an oxygen permeabilitymeasuring apparatus (OXTRAN, MOCON, USA). Measured data is tabulated inTable 1-1. TABLE 1-1 Total Moisture Oxygen Output trans- permea- permea-reduction mittance bility bility Ratio (%) (g/m²/24 hr) (cc/m²/24hr/atm) (%) Example 1 93 0.9 1.1 3 Example 2 92 0.6 0.5 2 Example 3 930.6 0.7 2 Example 4 93 0.9 1.1 1 Example 5 92 0.6 0.4 1 Example 6 93 0.60.7 1 Example 7 93 0.9 1.1 2 Example 8 92 0.6 0.5 5 Example 9 93 0.6 0.75 Example 10 91 0.1 0.4 1 Example 11 91 0.1 0.3 1 Comparative 89 25.0 80.0  18  Example 1 Comparative 93 27.0  28.0  15  Example 2 Comparative93 27.0  28.0  12  Example 3

[0247] In table 1-1, moisture permeability is expressed in a unit ofg/m²/day•40° C.•100% RH (relative humidity), and oxygen permeability isexpressed in a unit of cc/m²/day•23° C.•90% RH.

[0248] As obvious from Table 1-1, the protective sheets in Examples 1 to11 have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

[0249] The output reduction ratios of the solar battery modulesemploying the protective sheets in Examples 1 to 11 were low.

[0250] The protective sheets in Comparative examples 1 to 3 had hightotal transmittances, respectively. However, the moistureimpermeabilities and the oxygen impermeabilities of the protectivesheets in Comparative examples 1 to 3 were low. Consequently, the outputreduction ratios of the solar battery modules employing the protectivesheets in Comparative examples 1 to 3 were high.

[0251] As apparent from the foregoing description, the present inventiontakes notice of the properties of glass sheets that are used as thefront surface protective sheets of solar battery modules, uses afluorocarbon resin sheet as a base sheet, fabricates a protective sheetfor a solar battery module by forming a transparent, vitreous depositedinorganic oxide thin film, such as a silicon oxide thin film or analuminum oxide thin film, on one of the surfaces of the fluorocarbonresin sheet; the protective sheet thus fabricated is used as the frontsurface protective sheet or the back surface protective sheet of a solarbattery module; the solar battery module is fabricated by, for example,superposing the protective sheet as a front surface protective sheet, afiller layer, a film provided with solar cells, i.e., photovoltaiccells, a filler layer and an ordinary back surface protective sheet fora solar battery module in that order in a superposed structure with thedeposited inorganic oxide thin film facing inside, bringing thecomponent layers of the superposed structure into close contact byvacuum and bonding together those component layers by a laminationprocess using hot pressing; and the protective sheet transmits sunlightat a high transmittance, is excellent in strength, weather resistance,heat resistance, water resistance, light resistance, wind endurance,hailstorm resistance, chemical resistance, moisture resistance and soilresistance, has a high impermeability to moisture and oxygen, limitsperformance degradation due to aging to the least extent, very durable,has excellent protective ability, and can be used for the stablefabrication of a low-cost, safe solar battery module.

[0252] Other examples of the present invention and comparative exampleswill be described hereinafter.

Example 12

[0253] Front Surface Protective Sheet

[0254] A transparent 25 μm thick ETFE film was used as aweather-resistant film. A 500 Å thick silicon oxide (SiO_(x)) thin film(gas-barrier layer) was deposited on one surface of the ETFE. film by aPE-CVD process. A front surface protective sheet in Example 1 wasfabricated by forming a 250 μm thick adhesive layer of a compositematerial prepared by homogeneously mixing 100 parts by weight of anethylene-vinyl acetate copolymer having a vinyl acetate content of 35%by weight, 2 parts by weight of a crosslinking agent (DCP:dicumylperoxide) and 3 parts by weight of ultraviolet absorber(2,4-dihydroxybenzophenone) at 110° C. on the ETFE film by a calendercoating process.

[0255] Back Surface Protective Sheet

[0256] Two white 38 μm thick PVF films and a 20 μm thick aluminum foil(gas barrier layer) were laminated by a dry lamination process to form alaminated structure of (38 μm thick white PVF film)/(20 μm thickaluminum foil)/(38 μm thick white PVF film). A back surface protectivesheet in Example 1 was fabricated by forming a 250 μm thick compositeresin layer of a composite material prepared by homogeneously mixing 100parts by weight of an ethylene-vinyl acetate copolymer having a vinylacetate content of 35% by weight, 1 part by weight of a crosslinkingagent (DCP: dicumilperoxyd), 2 parts by weight of ultraviolet absorber(2,4-dihydroxybenzophenone) and 25 parts by weight of titanium oxide(white pigment) at 120° C. on the ETFE film by a calender coatingprocess.

Example 13

[0257] Front Surface Protective Sheet

[0258] A transparent 25 μm thick PVF film was used as aweather-resistant film. A 400 Å thick aluminum oxide thin film(gas-barrier layer) was deposited on one surface of the PVF film by aPVD process. A coating liquid of an inorganic-organic hybrid materialprepared by mixing 5 parts by weight of tetraethoxysilane and 95 partsby weight of an ethylene-vinyl alcohol copolymer was applied in acoating layer of 3 g/m² to the aluminum oxide thin film by a gravurecoating process, and the coating layer was hot-dried to complete acomposite gas-barrier layer. A 200 μm thick adhesive layer was formed onthe composite gas-barrier layer by extruding a composite resin preparedby homogeneously mixing 100 parts by weight of an ethylene-vinyl acetatehaving a vinyl acetate content of 30% by weight, 1.5 parts by weight ofa TBPH (2,5-dimethyl-2,5-di(t-butylperoxy)hexane), i.e., a crosslinkingagent, 2 parts by weight of TAC (triallylcyanurate), i.e., acrosslinking auxiliary, and three parts by weight of silane couplingagent at 110° C. on the composite gas-barrier layer by an extrusioncoating process to complete a front surface protective sheet in Example2 for a solar battery module.

[0259] Back Surface Protective Sheet

[0260] Two white 25 μm thick weather-resistant polyethyleneterephthalate films (hereinafter referred to as “white weather-resistantPET films”) and a 20 μm thick aluminum foil (gas barrier layer) werelaminated by a dry lamination process to form a laminated structure of(25 μm thick white weather-resistant PET film)/(20 μm thick aluminumfoil)/(25 μm thick white weather-resistant PET film). A 200 μm thickadhesive layer of a composite material prepared by homogeneously mixing100 parts by weight of an ethylene-vinyl acetate copolymer having avinyl acetate content of 30% by weight, 1.5 part by weight of a TBPH(2,5-dimethyl-2,5-di(t-butylperoxy)hexane), i.e., a crosslinking agent,1.5 parts by weight of TAC (triarylcyanurate), i.e., a crosslinkingauxiliary, and 2 parts by weight of silane coupling agent at 110° C. wasformed on one surface of the laminated structure by an extrusion coatingprocess to complete a back surface protective sheet in Example 13 for asolar battery module.

Comparative Example 4

[0261] Front Surface Protective Sheet

[0262] A front surface protective sheet in Comparative example 4 is thesame as the front surface protective sheet in Example 12, except thatthe deposited silicon oxide (SiO_(x)) thin film, i.e., a gas-barrierlayer, is omitted.

[0263] Back Surface Protective Sheet

[0264] A back surface protective sheet in Comparative example 4 is thesame as the back surface protective sheet in Example 12, except that thealuminum foil sandwiched between the two white PVF films is omitted.

[0265] Tests and Test Results

[0266] The front surface protective sheets and the back surfaceprotective sheets in Examples 12 and 13 and Comparative example 4 forsolar battery modules were subjected to the following tests.

[0267] Test results are tabulated in Tables 1-2 and 1-3.

[0268] (1) Moisture permeabilities in an atmosphere of 40° C. and 90% RHand oxygen permeabilities in an atmosphere of 25° C. and 100% RH of theprotective sheets were measured by a moisture permeability measuringapparatus (MOCON PERMATAN, Modern Control) and an oxygen permeabilitymeasuring apparatus (MOCON OXTRAN, Modern Control). Measured data isshown in Table 1-2. TABLE 1-2 Moisture Oxygen Test permeabilitypermeability Sample (g/m²/24 hr) (cc/m²/24 hr/atm) Example 12 Frontsurface 0.9 1.1 protective film Back surface ≦0.1 0.1 protective filmExample 13 Front surface 0.2 0.4 protective film Back surface ≦0.1 0.1protective film Comparative Front surface 18 43 Example 4 protectivefilm Back surface 4.9 5.2 protective film

[0269] In table 1-2, moisture permeability is expressed in a unit ofg/m²•atm•day, and oxygen permeability is expressed in a unit ofcc/m²•atm•day.

[0270] (2) Solar battery modules in Examples 12 and 13 and Comparativeexample 4 were fabricated by combining the front surface protectivesheets and the back surface protective sheets in Examples 12 and 13 andComparative example 4 with solar batteries employing a microcrystallinesilicon thin film formed by a PE-CVD process by a vacuum laminationprocess. The solar battery modules were subjected to tests to evaluatetheir performance and long-term stability, in which photoelectricconversion efficiency η (%) and fill factor (FF) were measured in aninitial state and in a state after irradiation with 1 sun, at 50° C. for2000 hr. Measured data is tabulated in Table 1-3. TABLE 1-3Characteristic of solar battery State after exposure Initial state to 1sun, 50° C., 2000 hr Conversion Conversion efficiency efficiency η (%)FF η (%) FF Example 12 10.5 0.75 10.3 0.73 Example 13 10.4 0.75 10.40.75 Comparative 10.5 0.75  9.0 0.65 Example 4

[0271] As obvious from the measured data shown in Tables 1-2 and 1-3,the protective sheets in Examples 12 and 13, which comprise thegas-barrier layer in addition to the weather-resistant film and theadhesive layers, are excellent in strength, weather resistance and heatresistance, have very small moisture permeabilities and oxygenpermeabilities, respectively, and are highly gas-impermeable.

[0272] The solar battery modules in Examples 12 and 13 fabricated bysandwiching the microcrystalline silicon thin film, which deteriorateseasily in an atmosphere containing moisture or oxygen, between theprotective sheets in Example 12 or 13 maintains satisfactoryphotoelectric conversion efficiency and FF after being irradiated by 1sun at 50° C. for 2000 hr. Thus, the solar battery modules in Examples12 and 13 are excellent in long-term stability.

[0273] Second Embodiment

[0274] Protective sheets for solar battery modules, and solar batterymodules in a second embodiment according to the present invention willbe described with reference to FIGS. 1 to 9 which have been used fordescribing the first embodiment.

[0275] Referring to FIG. 1, a protective sheet A in accordance with thepresent invention for a solar battery module has a basic structureconstructed by forming a deposited inorganic oxide thin film 2 on one ofthe surfaces of a weather-resistant sheet 1 of a cyclic polyolefinresin.

[0276] As shown in FIG. 3, a protective sheet A, in an example of thepresent invention for a solar battery module is formed by forming amultilayer film 4 consisting of at least two deposited inorganic oxidethin films 2 on one of the surfaces of a cyclic polyolefin resin sheet1.

[0277] As shown in FIG. 4 a protective sheet A₃ in another example ofthe present invention for a solar battery module comprises a cyclicpolyolefin resin sheet 1 and a composite film 5 formed on one of thesurfaces of the cyclic polyolefin resin sheet 1. The composite film 5consists of a first deposited inorganic oxide thin film 2 a formed onone of the surfaces of the cyclic polyolefin resin sheet 1 by a chemicalvapor deposition process, and a second deposited inorganic oxide thinfilm 2 b of an inorganic oxide different from that of the firstdeposited inorganic oxide film 2 a, formed on the first depositedinorganic oxide thin film 2 a by a physical vapor deposition process.

[0278] Those protective sheets are only examples of the protective sheetin accordance with the present invention and the present invention isnot limited thereto.

[0279] For example, in the protective sheet A₃ shown in FIG. 4, adeposited inorganic thin film may be formed first on the surface of thecyclic polyolefin resin sheet 1 a physical vapor deposition process, andthen another deposited inorganic oxide thin film may be formed by achemical vapor deposition process.

[0280] A solar battery module employing this protective sheet Aembodying the present invention and shown in FIG. 1 will be described byway of example. Referring to FIG. 5, a solar battery module T employsthe protective sheet A shown in FIG. 1 as its front surface protectivesheet 11(A). The solar battery module T is fabricated by superposing theprotective sheet 11(A), a filler layer 12, a photovoltaic layer 13 ofsolar cells, a filler layer 14 and a generally known back surfaceprotective sheet 15 in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The deposited inorganic oxide thinfilm 2 of the protective sheet 11 faces inside.

[0281] Another solar battery module T₁ shown in FIG. 6 employs theprotective sheet A shown in FIG. 1 as its back surface protective sheet16. The solar battery module T, is fabricated by superposing a generallyknown front surface protective sheet 17, a filler layer 12, aphotovoltaic layer 13 of solar cells, a filler layer 14 and theprotective sheet 16(A) in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a laminating process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The deposited inorganic oxide thinfilm 2 of the protective sheet 16 faces inside.

[0282] A third solar battery module T₂ shown in FIG. 7 employs theprotective sheet A shown in FIG. 1 as its front surface protective sheet11 and its back surface protective sheet 16. The solar battery module T₂is fabricated by superposing the front surface protective sheet 11(A), afiller layer 12, a photovoltaic layer 13 of solar cells, a filler layer14 and the protective sheet 16(A) in that order in a superposedstructure, and subjecting the superposed structure to a generally knownforming process, such as a lamination process, in which those componentlayers of the superposed structure are brought into close contact byvacuum and are bonded together by hot pressing. The deposited inorganicoxide thin film 2 of each of the protective sheets 11 and 16 facesinside.

[0283] The foregoing protective sheets in accordance with the presentinvention and the foregoing solar battery modules employing thoseprotective sheets are examples intended to illustrate the invention andnot to be construed to limit the scope of the invention.

[0284] For example, the protective sheets shown in FIGS. 3 and 4 can beapplied to solar battery modules of various types. The foregoing solarbattery modules may comprise additional layers for sunlight absorption,reinforcement or the like.

[0285] Materials for and methods of fabricating the protective sheets inaccordance with the present invention and the solar battery modulesemploying those protective sheets will be described. It is desirablethat the cyclic polyolefin resin film or sheet for the protective sheetsembodying the present invention and the solar battery modules employingthose protective sheets has a high sunlight transmittance because thesolar battery absorbs sunlight and generates power by its photovoltaiceffect.

[0286] It is desirable that the cyclic polyolefin resin film or sheet isexcellent in mechanical or chemical strength, excellent in weatherresistance, heat resistance, water resistance, light resistance, windendurance, hailstorm resistance, chemical resistance and piercingstrength. It is particularly desirable that the cyclic polyolefin resinfilm or sheet is excellent in weather resistance and moistureimpermeability that prevents the permeation of oxygen and the like, hasa high surface hardness, is excellent in soil resistance that preventsthe accumulation of soil and dust thereon, is very durable and has ahigh protective ability.

[0287] It is desirable that the cyclic polyolefin resin film or sheet iscapable of withstanding conditions for forming a deposited inorganicoxide thin film thereon, does not spoil the characteristics thereof andthe deposited inorganic oxide thin film deposited thereon, is capable offirmly adhering to the deposited inorganic oxide thin film and ofsatisfactorily holding the same thereon.

[0288] The present invention may employ transparent cyclic polyolefinfilms or sheets of, for example, cyclopentadiene, cyclopentadienederivatives, dicyclopentadiene, dicyclopentadiene derivatives,cyclohexadiene, cyclohexadiene derivatives, norbornadiene, norbornadienederivatives, polymers produced through the polymerization of cyclicdienes, copolymers of cyclic dienes and one or some of ethylene,propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene and thelike.

[0289] Among those transparent cyclic polyolefin resin films or sheets,film or sheets of polycyclopentadienes of cyclic dienes includingcyclopentadiene, cyclopentadiene derivatives, dicyclopentadiene,dicyclopentadiene derivatives, norbornadiene and norbornadienederivatives are excellent in properties including weather resistance,water resistance and transparency, and are particularly preferable fromthe view point of sunlight transmission.

[0290] The protective sheets of the solar battery modules using thecyclic polyolefin resin film or sheet utilizes the excellent propertiesof the cyclic polyolefin resin sheet including mechanical properties,optical properties and properties including weather resistance, heatresistance and water resistance, moisture impermeability, soilresistance, chemical resistance and piercing strength. The protectivesheet is equal to the glass sheet used as the conventional protectivesheet in optical properties and durability, has satisfactory mechanicalproperties, and is more flexible and lighter than the glass sheet,excellent in workability and easy to handle.

[0291] There is no possibility that the cyclic polyolefin film or sheetin accordance with the present invention causes environmentaldestruction of pollution when disposed of after use.

[0292] The cyclic polyolefin resin film or sheet in accordance with thepresent invention may be, for example, any one of films or sheets of theforegoing cyclic polyolefin resins formed by a film forming process,such as an extrusion process, a casting process, a T-die extrusionprocess, a cutting process, an inflation process or the like, any one ofmultilayer films or multilayer sheets of two or more kinds of theforegoing cyclic polyolefin resins formed by a coextrusion process, orany one of films or sheets formed by subjecting a mixture of a pluralityof kinds of the foregoing cyclic polyolefin resins to a film formingprocess. When necessary, the cyclic polyolefin resin film or sheet maybe a uniaxially or biaxially oriented film or sheet formed by subjectinga cyclic polyolefin resin film or sheet to a uniaxial or biaxialorientation process of a tenter system or a tubular film system.

[0293] The thickness of the cyclic polyolefin resin film or sheet is inthe range of about 12 to about 300 μm, desirably, in the range of about25 to about 200 μm.

[0294] It is desirable that the cyclic polyolefin resin film or sheet ofthe present invention has a visible light transmittance of 90% or above,preferably, 95% or above and a property to transmit all incidentsunlight and to absorb the same.

[0295] When forming the cyclic polyolefin resin film or sheet, variouscompounding ingredients and additives may be added to the cyclicpolyolefin resin to improve the workability, heat resistance, weatherresistance, strength, mechanical properties, dimensional stability,oxidation resistance, slipperiness, releasability, flame retardancy,antifungal property, electric properties, piercing strength and thelike. The amount of each of the compounding ingredients and theadditives is in the range of a very small percent to several tenspercent and may optionally be determined according to the purpose.

[0296] The cyclic olefin resin may contain commonly known additives,such as a lubricant, a crosslinking agent, an oxidation inhibitor, anultraviolet absorber, a light stabilizer, a filler, a reinforcingmaterial, reinforcing fibers, an antistatic agent, a flame retarder, aflame-resistant agent, a foaming agent, an antifungus agent, a pigmentand the like. The cyclic polyolefin resin may further contain modifiers.

[0297] In the present invention, it is preferable to use a cyclicpolyolefin resin film or sheet of a composite cyclic polyolefin resinproduced by preparing a mixture of a cyclic polyolefin resin, anoxidation inhibitor, an ultraviolet absorber or one or a plurality ofkinds of reinforcing fibers, and kneading the mixture to improve theweather resistance, strength, piercing strength and the like.

[0298] When necessary, a surface-treated layer 3 may be formed in asurface of the fluorocarbon resin sheet by a surface pretreatmentprocess to improve the adhesion between the surface of the cyclicpolyolefin film or sheet and the deposited inorganic oxide thin film.

[0299] The surface-treated layer 3 may be formed by, for example, acorona discharge treatment, an ozone treatment, a low-temperature plasmatreatment using oxygen gas or nitrogen gas, a glow discharge treatment,an oxidation treatment using a chemical or the like. The surface-treatedlayer 3 may be a corona-treated layer, an ozone-treated layer, aplasma-treated layer, an oxidized layer or the like.

[0300] The surface pretreatment of the cyclic polyolefin resin film orsheet is a method of improving adhesion between the cyclic polyolefinresin film or sheet and the deposited inorganic oxide thin film. Thesurface of the cyclic polyolefin resin film or sheet is finished by thesurface pretreatment to improve the adhesion between the cyclicpolyolefin resin film or sheet and the deposited inorganic oxide thinfilm . The improvement of adhesion can be achieved by forming, insteadof forming the surface-treated layer, a layer of a primer, anundercoater, an anchoring agent, an adhesive or a deposited undercoatingmaterial.

[0301] Suitable materials for forming the coating layer are, forexample, composite resins containing a polyester resin, a polyamideresin, a polyurethane resin, an epoxy resin, a phenolic resin, a(meta)acrylic resin, a polyvinyl acetate resin, a polyolefin resin suchas a polyethylene, a polypropylene or a copolymer or a resin obtained bymodifying one of those resins, a cellulose resin or the like as aprincipal component of a vehicle.

[0302] In the present invention, the composite resin may contain anultraviolet absorber and/or an oxidation inhibitor for weatherresistance improvement.

[0303] The composite resin may contain one or a plurality of theforegoing ultraviolet absorbers.

[0304] The composite resin may contain one or a plurality of theforegoing oxidation inhibitors.

[0305] The ultraviolet absorber and/or the oxidation inhibitor contentis dependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

[0306] The coating layer may be formed of a coating material of, forexample, a solvent type, an aqueous type or an emulsion type by a rollercoating process, a gravure coating process, a kiss-roll coating processor the like. The coating layer may be formed by a coating processsubsequent to a resin film or sheet forming process or a biaxialorientation process, or by an in-line coating process included in thefilm forming process or the biaxial orientation process.

[0307] The surface-treated layer may be formed on one surface of thecyclic polyolefin resin film or sheet to protect the cyclic polyolefinresin film or sheet from vapor deposition conditions for forming thedeposited inorganic oxide thin film, to suppress yellowing,deterioration, shrinkage or cohesive failure in a surface layer or aninner layer of the cyclic polyolefin resin film or sheet, and to improvethe adhesion between the cyclic polyolefin resin film or sheet and thedeposited inorganic oxide thin film. The surface-treated layer, i.e., adeposition-resistant protective film, such as a deposited inorganicoxide thin film, may be formed by, for example, a chemical vapordeposition process (CVD process), such as a plasma chemical vapordeposition process, a thermal chemical vapor deposition process or aphotochemical vapor deposition process, or a physical vapor depositionprocess (PVD process), such as a vacuum evaporation process, asputtering process or an ion plating process.

[0308] The thickness of the deposition-resistant protective film ofsilicon oxide or the like may be less than 150 Å. Thedeposition-resistant protective film may be a nonbarrier film not havingany barrier effect to inhibit the permeation of moisture and oxygen gas.Concretely, the thickness of the deposition-resistant protective film isin the range of about 10 to about 100 Å, more preferably, in the rangeof about 20 to 80 Å, more preferably, in the range of about 30 to about60 Å.

[0309] If the thickness is greater than 150 Å, more concretely 100 Å, 80Å or 60 Å, the cyclic polyolefin resin film or sheet is exposed tosevere deposition conditions. Consequently, the cyclic polyolefin resinfilm or sheet turns yellow, cohesive failure occurs, the formation of asatisfactory deposition-resistant protective film becomes difficult, andcracks develop in the film. If the thickness is less than 10 Å, 20 Å or30 Å, the film is incapable of functioning as an effectivedeposition-resistant protective film.

[0310] When the cyclic polyolefin resin film or sheet forms theoutermost layer of a solar battery, the cyclic polyolefin resin film orsheet may be an embossed film or sheet having an embossed surface orembossed surfaces finished by an embossing process to provide the cyclicpolyolefin resin film or sheet with a sunlight diffusing effect or anantireflection effect.

[0311] The embossed surface may be such as having irregularities ofsizes in the range of a submicron size to several hundreds micrometer.The irregularities may be of any suitable shape, such as a pyramidalshape, a V-shape or a plaid-shape.

[0312] The deposited inorganic oxide thin film may be formed by thecontinuous vacuum evaporation system shown in FIG. 8.

[0313] The low-temperature plasma chemical vapor deposition process forforming the deposited inorganic oxide thin film may be carried out bythe low-temperature plasma chemical vapor deposition system shown inFIG. 9.

[0314] When fabricating a solar battery module, the reinforcing fibersmay be, for example, glass fibers or filaments, carbon fibers orfilaments, aramid fibers or filaments, polyamide fibers or filaments,polyester fibers or filaments, natural fibers or the like. Thereinforcing fibers or filaments, or a nonwoven fabric of the reinforcingfibers or filaments may be used for forming a fiber-reinforcing layer.

[0315] It is also possible to form the fiber-reinforced layer bypreparing a mixture of the reinforcing fibers or filaments, such as theforegoing glass fibers or filaments, carbon fibers or filaments, aramidfibers or filaments, polyamide fibers or filaments, polyester fibers orfilaments, natural fibers or the like, or a nonwoven fabric or a sheetresembling a nonwoven fabric of the reinforcing fibers or filaments, anda resin for forming the filler layer, such as one of fluorocarbonresins, ethylene-vinyl acetate resins, methacrylate copolymers,polyethylene resins, polypropylene resins, modified polyolefin resinsproduced by modifying polyolefin resins, such as polyethylene resins orpolypropylene resins, by an unsaturated carboxylic acid, such as acrylicacid, itaconic acid, maleic acid or fumaric acid, cyclic polyolefinresins, polyvinyl butyral resins, silicone resins, epoxy resins,(meta)acrylic resins and the like, kneading the mixture, and forming afilm of the kneaded mixture.

EXAMPLES

[0316] Examples of the second embodiment will concretely be describedhereinafter.

Example 1

[0317] (1) A roll of a 100 μm thick polydicyclopentadiene resin sheet,i.e., base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polydicyclopentadiene resin sheet was unwoundand wound around a coating drum and a 500 Å thick deposited aluminumoxide thin film was deposited on a treated surface of thepolydicyclopentadiene resin sheet treated for adhesion improvement by areactive vacuum evaporation process of an electron beam (EB) heatingsystem. Aluminum was used as an evaporation source and oxygen gas wassupplied to the continuous vacuum evaporation system.

[0318] Deposition conditions:

[0319] Evaporation source: Aluminum

[0320] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0321] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0322] EB power: 40 kW

[0323] Sheet moving speed: 600 m/min

[0324] (2) A protective sheet in accordance with the present inventionfor a solar battery module was completed by subjecting the 500 Å thickdeposited aluminum oxide thin film formed on the surface of thepolydicyclopentadiene resin sheet to a glow-discharge plasma process toform a plasma-processed surface. The glow-discharge plasma process wascarried out by a glow-discharge plasma producing apparatus of 1500 W inplasma output immediately after the deposition of the 500 Å thickdeposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

[0325] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated. The protective sheet, a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and a 50 μm thick biaxially oriented polyethylene terephthalatefilm were superposed in that order with the plasma-processed depositedaluminum oxide thin film facing inside and the surface of the 38 μmthick biaxially oriented polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the front surfaceprotective sheet. Those component layers were laminated by usingadhesive layers of an acrylic resin to complete a solar battery module.

[0326] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene resin sheet was used instead of the 100 μm thickpolydicyclopentadiene resin sheet as the base sheet.

Example 2

[0327] (1) A roll of a 100 μm thick polydicyclopentadiene resin sheet,i.e., base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 500 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polydicyclopentadiene resin sheettreated for adhesion improvement under the following conditions.

[0328] Deposition conditions:

[0329] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (Unit: slm)

[0330] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0331] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0332] Power supplied to cooling electrode drum: 20 kW

[0333] Film moving speed: 80 m/min

[0334] Surface for vapor deposition: Corona-processed surface

[0335] (2) A protective sheet in accordance with the present inventionfor a solar battery module was completed by subjecting the 500 Å thickdeposited silicon oxide thin film formed on the surface of thepolydicyclopentadiene resin sheet to a corona discharge process to forma corona-processed surface and to increase the surface tension of thedeposited silicon oxide thin film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

[0336] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the corona-processed deposited silicon oxide thinfilm facing inside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0337] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene resin sheet was used instead of the 100 μm thickpolydicyclopentadiene resin sheet.

Example 3

[0338] (1) A roll of a 300 μm thick polydicyclopentadiene resin sheetcontaining an ultraviolet absorber was mounted on a feed roll of aplasma chemical vapor deposition system. A 500 Å thick deposited siliconoxide thin film was deposited on a treated surface of thepolydicyclopentadiene resin sheet treated for adhesion improvement underthe following conditions.

[0339] Deposition conditions:

[0340] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (Unit: slm)

[0341] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0342] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0343] Power supplied to cooling electrode drum: 20 kW

[0344] Film moving speed: 80 m/min

[0345] Surface for deposition: Corona-processed surface

[0346] The surface of the 500 Å thick deposited silicon oxide thin filmformed on the polydicyclopentadiene resin sheet was subjected to acorona discharge process to form a corona-processed surface and toincrease the surface tension of the deposited silicon oxide thin filmfrom 35 dyne to 60 dyne. Corona discharge power was 10 kW and the sheetwas moved at a moving speed of 100 m/min.

[0347] (2) A roll of the polydicyclopentadiene resin sheet provided withthe corona-processed deposited silicon oxide thin film was mounted on afeed roll of a continuous vacuum evaporation system. Thepolydicyclopentadiene resin sheet was unwound and wound around a coatingdrum and a 500 Å thick deposited aluminum oxide thin film was depositedon the corona-processed surface of the deposited silicon oxide thin filmformed on the polydicyclopentadiene resin sheet by a reactive vacuumevaporation process of an electron beam (EB) heating system. Aluminumwas used as an evaporation source and oxygen gas was supplied to thecontinuous vacuum evaporation system.

[0348] Deposition conditions:

[0349] Evaporation source: Aluminum

[0350] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0351] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0352] EB power: 40 kW

[0353] Film moving speed: 600 m/min

[0354] A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 500 Å thickdeposited aluminum oxide thin film formed on the surface of thepolydicyclopentadiene resin sheet to a glow-discharge plasma process toform a plasma-processed surface. The glow-discharge plasma process wascarried out by a glow-discharge plasma producing apparatus of 1500 W inplasma output immediately after the deposition of the 500 Å thickdeposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

[0355] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. Theprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the plasma-processed deposited aluminum oxide thin film facinginside and the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet. Those component layers were laminated byusing adhesive layers of an acrylic resin to complete a solar batterymodule.

[0356] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 300 μm thickpolycyclopentadiene resin sheet containing an ultraviolet absorber wasused instead of the 300 μm thick polydicyclopentadiene resin sheetcontaining an ultraviolet absorber and used as the base sheet.

Example 4

[0357] (1) Protective sheets that are the same as the protective sheetin Example 1 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the solar cells facing the frontsurface protective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0358] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 100 μm thick polycyclopentadieneresin sheets were used instead of the 100 μm thick polydicyclopentadieneresin sheets.

Example 5

[0359] (1) Protective sheets that are the same as the protective sheetin Example 2 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited silicon oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0360] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 100 μm thick polycyclopentadieneresin sheets were used instead of the 100 μm thick polydicyclopentadieneresin sheets.

Example 6

[0361] (1) Protective sheets that are the same as the protective sheetin Example 3 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0362] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 300 μm thick polycyclopentadieneresin sheets containing an ultraviolet absorber were used instead of the300 μm thick polydicyclopentadiene resin sheet containing theultraviolet absorber.

Example 7

[0363] (1) A protective sheet that is the same as the protective sheetin Example 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 3 mm thickglass sheet, and laminating those component layers by using adhesivelayers of an acrylic resin.

[0364] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet was used instead of the 100 μm thick polydicyclopentadieneresin sheet.

Example 8

[0365] (1) A protective sheet that is the same as the protective sheetin Example 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecorona-processed deposited silicon oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

[0366] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet was used instead of the 100 μm thick polydicyclopentadieneresin sheet.

Example 9

[0367] (1) A protective sheet that is the same as the protective sheetin Example 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

[0368] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet was used instead of the 100 μm thick polydicyclopentadieneresin sheet.

Example 10

[0369] (1) A roll of a 100 μm thick polydicyclopentadiene resin sheetcontaining an ultraviolet absorber comprising ultrafine titanium oxidepowder, and glass fibers was mounted on a feed roll of a plasma chemicalvapor deposition system. A 50 Å thick deposited silicon oxide thin filmas a deposition-resistant protective film was deposited on a surface ofthe polydicyclopentadiene resin sheet under the following conditions.

[0370] Deposition conditions:

[0371] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=5/5/5 (Unit: slm)

[0372] Vacuum in vacuum chamber: 7.0×10⁻⁶ mbar

[0373] Vacuum in deposition chamber: 3.8×10⁻² mbar

[0374] Power supplied to cooling electrode drum: 15 kW

[0375] Sheet moving speed: 100 m/min

[0376] (2) A roll of the polydicyclopentadiene resin sheet provided withthe deposition-resistant protective film was mounted on a feed roll of aplasma chemical vapor deposition system. A 800 Å thick deposited siliconoxide thin film was deposited on the deposition-resistant protectivefilm formed on the polydicyclopentadiene resin sheet.

[0377] Deposition conditions:

[0378] Evaporation source: Aluminum

[0379] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0380] Vacuum in deposition chamber: 6.0×10−2 mbar

[0381] Power supplied to cooling electrode drum: 20 kW

[0382] Film moving speed: 80 m/min

[0383] A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 800 Å thickdeposited silicon oxide thin film to a corona discharge process to forma corona-processed surface and to increase the surface tension of thedeposited silicon oxide thin film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

[0384] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. Theprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the corona-processed deposited silicon oxide thin film facinginside and the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet. Those component layers were laminated byusing adhesive layers of an acrylic resin to complete a solar batterymodule.

[0385] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers was usedinstead of the 100 μm thick polydicyclopentadiene resin sheet containingan ultraviolet absorber comprising ultrafine titanium oxide powder, andglass fiber.

Example 11

[0386] (1) A roll of the polydicyclopentadiene resin sheet in Example 10provided with the deposition-resistant protective film was mounted on afeed roll of a continuous vacuum evaporation system. Thepolydicyclopentadiene resin sheet was unwound and wound around a coatingdrum and a 800 Å thick deposited aluminum oxide thin film was depositedon the deposition-resistant protective film by a reactive vacuumevaporation process of an electron beam (EB) heating system. Aluminumwas used as an evaporation source and oxygen gas was supplied to thecontinuous vacuum evaporation system.

[0387] Deposition conditions:

[0388] Evaporation source: Aluminum

[0389] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0390] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0391] EB power: 40 kw

[0392] Film moving speed: 600 m/min

[0393] A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 800 Å thickdeposited aluminum oxide thin film to a glow-discharge plasma process toform a plasma-processed surface. The glow-discharge plasma process wascarried out by a glow-discharge plasma producing apparatus of 1500 W inplasma output immediately after the deposition of the 800 Å thickdeposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

[0394] (2) The protective sheet thus fabricated was used as a frontsurface protective sheet. A 400 μm thick ethylene-vinyl acetatecopolymer sheet was laminated to the plasma-processed surface of thedeposited aluminum oxide thin film with an adhesive layer of an acrylicresin.

[0395] A 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderon the ethylene-vinyl acetate copolymer sheet laminated to theprotective sheet with the he surface of the 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet.Those component layers were laminated by using adhesive layers of anacrylic resin to complete a solar battery module.

[0396] (3) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers was usedinstead of the 100 μm thick polydicyclopentadiene resin sheet containingan ultraviolet absorber comprising ultrafine titanium oxide powder, andglass fibers.

Example 12

[0397] (1) A 100 μm thick polydicyclopentadiene resin sheet containingan ultraviolet absorber comprising ultrafine titanium oxide powder, andglass fibers was used. One of the surfaces of the polydicyclopentadieneresin sheet was processed by an embossing process using an embossingroller to form an embossed surface provided with pyramidal projectionsof 1 μm in size.

[0398] A roll of the polydicyclopentadiene resin sheet having theembossed surface was mounted on a feed roll of a continuous vacuumevaporation system. The polydicyclopentadiene resin sheet was unwoundand wound around a coating drum and a 50 Å thick deposited aluminumoxide thin film as a deposition-resistant protective film was depositedon the other surface not embossed of the polydicyclopentadiene resinsheet by a reactive vacuum evaporation process of an electron beam (EB)heating system. Aluminum was used as an evaporation source and oxygengas was supplied to the continuous vacuum evaporation system.

[0399] Deposition conditions:

[0400] Evaporation source: Aluminum

[0401] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0402] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0403] EB power: 20 kW

[0404] Film moving speed: 500 m/min

[0405] (2) A protective sheet in accordance with the present inventionfor a solar battery module was completed by forming a 800 Å thickdeposited aluminum oxide thin film on the deposition-resistantprotective film formed on the unembossed surface of thepolydicyclopentadiene resin sheet by a reactive vacuum evaporationprocess of an electron beam (EB) heating system similar to that that inExample 1, and subjecting the 800 Å thick deposited aluminum oxide thinfilm to a plasma process to form a plasma-processed surface.

[0406] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. Theprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the plasma-processed surface of the deposited aluminum oxide thinfilm facing inside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0407] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers and havingan embossed surface was used instead of the 100 μm thickpolydicyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers and havingthe embossed surface.

Example 13

[0408] (1) Protective sheets that are the same as the protective sheetin Example 10 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the corona-processed deposited silicon oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the solar cells facing the frontsurface protective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0409] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheets containing an ultraviolet absorber comprising ultrafinetitanium oxide powder, and glass fibers were used instead of the 100 μmthick polydicyclopentadiene resin sheets containing an ultravioletabsorber comprising ultrafine titanium oxide powder, and glass fibersface.

Example 14

[0410] (1) Protective sheets that are the same as the protective sheetin Example 11 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. A 400 μm thickethylene-vinyl acetate copolymer sheet was laminated to theplasma-processed surface of the deposited aluminum oxide thin film ofthe front surface protective sheet with an adhesive layer of an acrylicresin to form a first laminated structure.

[0411] A 400 μm thick ethylene-vinyl acetate copolymer sheet waslaminated to the plasma-processed surface of the deposited aluminumoxide thin film of the back surface protective sheet with an adhesivelayer of an acrylic resin to form a second laminated structure.

[0412] A 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells was sandwichedbetween the first and the second laminated structure with the 400 μmthick ethylene-vinyl acetate copolymer sheets contiguous with the 38 μmthick biaxially oriented polyethylene terephthalate film and with thesurface of the 38 μm thick biaxially oriented polyethylene terephthalatefilm facing the front surface protective sheet.

[0413] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheets containing an ultraviolet absorber comprising ultrafinetitanium oxide powder, and glass fibers were used instead of the 100 μmthick polydicyclopentadiene resin sheets containing an ultravioletabsorber comprising ultrafine titanium oxide powder, and glass fibersface.

Example 15

[0414] (1) Protective sheets that are the same as the protective sheetin Example 12 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin films of the front surface and the back surface protective sheetfacing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0415] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 100 μm thick embossedpolycyclopentadiene resin sheets containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers were usedinstead of the 100 μm thick embossed polydicyclopentadiene resin sheetscontaining the ultraviolet absorber comprising ultrafine titanium oxidepowder, and glass fibers.

Example 16

[0416] (1) A protective sheet that is the same as the protective sheetin Example 10 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the corona-processed deposited silicon oxidethin film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 3 mm thickglass sheet, and laminating those component layers by using adhesivelayers of an acrylic resin.

[0417] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet containing an ultraviolet absorber comprising ultrafinetitanium oxide powder, and glass fibers was used instead of the 100 μmthick polydicyclopentadiene resin sheet containing an ultravioletabsorber comprising ultrafine titanium oxide powder, and glass fibers.

Example 17

[0418] (1) A protective sheet that is the same as the protective sheetin Example 11 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

[0419] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet containing an ultraviolet absorber comprising ultrafinetitanium oxide powder, and glass fibers was used instead of the 100 μmthick polydicyclopentadiene resin sheet containing an ultravioletabsorber comprising ultrafine titanium oxide powder, and glass fibers.

Example 18

[0420] (1) A protective sheet that is the same as the protective sheetin Example 11 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin. (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick embossedpolycyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers was usedinstead of the 100 μm thick embossed polydicyclopentadiene resin sheetcontaining an ultraviolet absorber comprising ultrafine titanium oxidepowder, and glass fibers.

Comparative Example 1

[0421] A 3 mm thick glass sheet was used as a base sheet for a frontsurface protective sheet for a solar battery module. The solar batterymodule was fabricated by superposing the 3 mm thick glass sheet, a 400μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and a 50 μm thick biaxially oriented polyethyleneterephthalate film in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the glass sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

Comparative Example 2

[0422] A 50 μm thick polyvinyl fluoride sheet (PVF sheet) was used as abase sheet for a front surface protective sheet for a solar batterymodule. The solar battery module was fabricated by superposing the 50 μmthick polyvinyl fluoride sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing the 50μm thick polyvinyl fluoride sheet, and laminating those component layersby using adhesive layers of an acrylic resin.

Comparative Example 3

[0423] Two 50 μm thick polyvinyl fluoride sheets (PVF sheets) were usedas base sheets for a front surface protective sheet and a back surfaceprotective sheet for a solar battery module. The solar battery modulewas fabricated by superposing one of the two 50 μm thick polyvinylfluoride sheets (PVF sheets), a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theother 50 μm thick polyvinyl fluoride sheet (PVF sheet) in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing the 50μm thick polyvinyl fluoride sheet serving as the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0424] Experiments

[0425] The protective sheets in Examples 1 to 18 and in Comparativeexamples 1 to 3 were subjected to total transmittance measurement. Thesolar battery modules in Examples 1 to 18 and Comparative examples 1 to3 were subjected to solar battery module evaluation tests.

[0426] (1) Total Transmittance Measurement

[0427] Total transmittance (%) of each of the protective sheets inExamples 1 to 18 and Comparative examples 1 to 3 against the totaltransmittance of the base sheet as a reference total transmittance wasmeasured by a color computer.

[0428] (2) Solar Battery Module Evaluation Tests

[0429] The solar battery modules were subjected to environmental testsin conformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

[0430] (3) Moisture Permeability and Oxygen Permeability

[0431] The moisture permeabilities of the protective sheets in Examples1 to 18 and Comparative examples 1 to 3 were measured in an atmosphereof 40° C. and 90% RH by a moisture permeability measuring apparatus(PERMATRAN, MOCON, USA). The oxygen permeabilities of the protectivesheets in Examples 1 to 18 and Comparative examples 1 to 3 were measuredin an atmosphere of 23° C. and 90% RH by an oxygen permeabilitymeasuring apparatus (OXTRAN, MOCON, USA). Measured data is tabulated inTable 2-1. TABLE 2-1 Total Moisture Oxygen Output trans- permea- permea-reduction mittance bility bility Ratio (%) (g/m²/24 hr) (cc/m²/24hr/atm) (%) Example 1 92 0.5 5.3 4 Example 2 91 0.2 2.0 3 Example 3 910.1 1.1 2 Example 4 92 0.5 4.9 2 Example 5 91 0.2 1.8 2 Example 6 91 0.11.0 1 Example 7 92 0.5 5.1 3 Example 8 91 0.2 2.1 4 Example 9 91 0.1 1.14 Example 10 90 0.3 4.5 3 Example 11 90 0.2 2.0 3 Example 12 90 0.1 0.92 Example 13 90 0.3 3.9 2 Example 14 89 0.2 1.5 2 Example 15 91 0.3 0.81 Example 16 90 0.2 0.7 1 Example 17 90 0.1 0.6 1 Example 18 89 0.1 0.91 Comparative 89 15.5  40.3  14  Example 1 Comparative 93 26.3  27.7 15  Example 2 Comparative 93 26.3  27.7  12  Example 3

[0432] In table 2-1, total transmittance is expressed in a unit of %,moisture permeability is expressed in a unit of g/m²/day•40° C.•100% RH,oxygen permeability is expressed in a unit of cc/m²/day•23° C.•90% RH,and output reduction ratio is expressed in a unit of %.

[0433] As obvious from Table 2-1, the protective sheets in Examples 1 to18 have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

[0434] The output reduction ratios of the solar battery modulesemploying the protective sheets in Examples 1 to 18 were low.

[0435] The protective sheets in Comparative examples 1 to 3 had hightotal transmittances, respectively. However, the moistureimpermeabilities and the oxygen impermeabilities of the protectivesheets in Comparative examples 1 to 3 were low. Consequently, the outputreduction ratios of the solar battery modules employing the protectivesheets in Comparative examples 1 to 3 were high.

[0436] As apparent from the foregoing description, the present inventionuses a cyclic polyolefin resin film or sheet as a base sheet, fabricatesa protective sheet for a solar battery module by forming a transparent,vitreous deposited inorganic oxide thin film, such as a silicon oxidethin film or an aluminum oxide thin film, on one of the surfaces of thecyclic polyolefin resin film or sheet; the protective sheet thusfabricated is used as the front surface protective sheet or the backsurface protective sheet of a solar battery module; the solar batterymodule is fabricated by, for example, superposing the protective sheetas a front surface protective sheet, a filler layer, a film providedwith solar cells, i.e., photovoltaic cells, a filler layer and a backsurface protective sheet for a solar battery module in that order in asuperposed structure with the deposited inorganic oxide thin film facinginside, bringing the component layers of the superposed structure intoclose contact by vacuum and bonding together those component layers by alamination process using hot pressing; and the protective sheet isexcellent in sunlight transmittance, strength, weather resistance, heatresistance, water resistance, light resistance, wind endurance,hailstorm resistance, chemical resistance, moisture resistance, soilresistance and piercing strength, has a high impermeability to moistureand oxygen, limits performance degradation due to aging to the leastextent, very durable, has excellent protective ability, and can be usedfor the stable fabrication of a low-cost, safe solar battery module.

[0437] The materials mentioned in the description of the firstembodiment are applicable to the second embodiment.

[0438] Third Embodiment

[0439] The present invention will be described hereinafter withreference to the accompanying drawings.

[0440] In this description, the term “sheet” is used in its broad senseto denote both sheets and films, and the term “film” is used in itsbroad sense to denote both sheets and films.

[0441] Protective sheets in accordance with the present invention forsolar battery modules and solar battery modules employing the protectivesheets will be described with reference to the accompanying drawings.FIGS. 10, 11 and 12 are typical sectional views of protective sheets inexamples in a third embodiment according to the present invention for asolar battery module, and FIGS. 13, 14 and 15 are typical sectionalviews of solar battery modules employing the protective sheet shown inFIG. 10.

[0442] Referring to FIG. 10, a protective sheet A embodying the presentinvention for a solar battery module has a basic structure comprising aplastic sheet (weather-resistant sheet) 1, a deposited inorganic oxidefilm 2 formed on one of the surfaces of the plastic sheet 1, and acoating film 103 of a condensation polymer produced through thehydrolysis of a silicon compound and formed on the deposited inorganicoxide film 2.

[0443] As shown in FIG. 11, a protective sheet A₁ in an example of thethird embodiment for a solar battery module comprises a plastic sheet 1,a multilayer film 4 consisting of at least two deposited inorganic oxidefilms 2 and formed on one of the surfaces of the plastic sheet 1, and acoating film 103 of a condensation polymer produced through thehydrolysis of a silicon compound and formed on the deposited inorganicoxide film 2 of the multilayer film 4.

[0444] As shown in FIG. 12 a protective sheet A₃ in a third example ofthe third embodiment for a solar battery module comprises a plasticsheet 1, a composite film 5 consisting of a first deposited inorganicoxide film 2 a formed on one of the surfaces of the plastic sheet 1 by achemical vapor deposition process and a deposited inorganic oxide film 2b formed on the deposited inorganic oxide film 2 a by a physical vapordeposition process, and formed on one of the surfaces of the plasticfilm 1, and a coating film 13 of a condensation polymer produced throughthe hydrolysis of a silicon compound and formed on the depositedinorganic oxide film.

[0445] Those protective sheets are only examples of the protective sheetin the first embodiment and the present invention is not limitedthereto.

[0446] For example, in the protective sheet A₂ shown in FIG. 12, adeposited inorganic oxide film may be formed first on the surface of theplastic sheet 1 by a physical vapor deposition process, and then anotherdeposited inorganic oxide film may be formed by a chemical vapordeposition process.

[0447] A solar battery module employing this protective sheet Aembodying the present invention and shown in FIG. 10 will be describedby way of example. Referring to FIG. 13, a solar battery module Temploys the protective sheet A shown in FIG. 10 as its front surfaceprotective sheet 11. The solar battery module T is fabricated bysuperposing the front surface protective sheet 11(A), a filler layer 12,a photovoltaic layer 13 of solar cells, a filler layer 14 and agenerally known back surface protective sheet 15 in that order in asuperposed structure, and subjecting the superposed structure to agenerally known forming process, such as a lamination process, in whichthose component layers of the superposed structure are brought intoclose contact by vacuum and are bonded together by hot pressing. Thecoating film 103 of the front surface protective sheet 11 faces inside.

[0448] Another solar battery module T₁ shown in FIG. 14 employs theprotective sheet A shown in FIG. 1 as its back surface protective sheet16. The solar battery module T₁ is fabricated by superposing a generallyknown front surface protective sheet 17, a filler layer 12, aphotovoltaic layer 13 of solar cells, a filler layer 14 and the backsurface protective sheet 16(A) in that order in a superposed structure,and subjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The coating film 103 of theprotective sheet 16 faces inside.

[0449] A third solar battery module T₂ shown in FIG. 15 employs theprotective sheet A shown in FIG. 10 as its front surface protectivesheet 11 and its back surface protective sheet 16. The solar batterymodule T₂ is fabricated by superposing the front surface protectivesheet 11(A), a filler layer 12, a photovoltaic layer 13 of solar cells,a filler layer 14 and the protective sheet 16(A) in that order in asuperposed structure, and subjecting the superposed structure to agenerally known forming process, such as a lamination process, in whichthose component layers of the superposed structure are brought intoclose contact by vacuum and are bonded together by hot pressing. Thecoating film 103 of each of the protective sheets 11 and 16 facesinside.

[0450] The foregoing protective sheets in accordance with the presentinvention and the foregoing solar battery modules employing thoseprotective sheets are examples intended to illustrate the invention andnot to be construed to limit the scope of the invention.

[0451] For example, the protective sheets shown in FIGS. 11 and 12 canbe applied to solar battery modules of various types. The foregoingsolar battery modules may comprise additional layers for sunlightabsorption, reinforcement or the like. Basically, the plastic sheet(weather-resistant sheet) 1 for forming the protective sheet inaccordance with the present invention and the solar battery module maybe a film or sheet capable of withstanding deposition conditions forforming the deposited inorganic oxide film or coating conditions forforming the coating film, excellent in adhesion to the depositedinorganic oxide film or the coating film, capable of satisfactorilyholding the film without adversely affecting the characteristics ofthose films, excellent in sunlight transmittance that affect theabsorption of sunlight by a solar battery and the photovoltaic powergeneration of a solar battery, excellent in strength, weatherresistance, heat resistance, water resistance, light resistance, windendurance, hailstorm resistance and chemical resistance, having a highimpermeability to moisture and oxygen, limiting performance degradationto the least extent, very durable, and having excellent protectiveability. Those resin films or sheets may be those of, for example,polyethylene resins, polypropylene resins, cyclic polyolefin resins,polystyrene resins, acrylonitrile-styrene copolymers (AS resins),acrylonitrile-butadiene-styrene copolymers (ABS resins), polyvinylchloride resins, fluorocarbon resins poly(meta)acrylic resins,polycarbonate resins, polyester resins, such as polyethyleneterephthalate and polyethylene naphthalate, polyamide resins, such asnylons, polyimide resins, polyamidimide resins, polyaryl phthalateresins, silicone resins, polysulfone resins, polyphenylene sulfideresins, polyester sulfone resins, polyurethane resins, acetal resins,cellulose resins and the like.

[0452] Sheets of fluorocarbon resins, cyclic polyolefin resins,polycarbonate resins, poly(meta)acrylic resins and polyester resins areparticularly preferable.

[0453] According to the present invention, it is particularly preferableto use transparent films or sheets of, for example,polytetrafluoroethylene (PTFE), perfluoroalcoxy resins (PFA), i.e.,copolymers of tetrafluoroethylene and perfluoroalkylvinyl ether,copolymers of tetrafluoroethylene and hexafluoropropylene (FEP),copolymers of tetrafluoroethylene, perfluoroalkylvinyl ether andhexafluoropropylene (EPE), copolymers of tetrafluoroethylene andethylene or propylene (ETFE), polychlorotrifluoroethylene resins (PCTFE)copolymers of ethylene and chlorotrifluoroethylene (ECTFE), vinylidenefluoride resins (PVDF), and one or some of fluorocarbon resins, such asvinyl fluoride resins (PVF).

[0454] Among those fluorocarbon resin sheets, sheets of polyvinylfluoride resins (PVF) or copolymers of tetrafluoroethylene and ethyleneor propylene (ETFE) are particularly preferable from the view point oftransparency and sunlight transmittance.

[0455] According to the present invention, it is particularly preferableto use cyclic polyolefin resin sheets of, for example, cyclopentadieneand its derivatives, dicyclopentadiene and its derivatives,cyclohexadiene and its derivatives, norbornadiene and its derivatives,polymers of cyclic diene monomers, and copolymers of cyclic dienemonomers and one or some of propylene, 4-methyl-1-pentene, styrene,butadiene, isoprene and olefin monomers.

[0456] According to the present invention, it is particularly preferableto use, among the foregoing transparent cyclic polyolefin resin sheets,transparent cyclic polyolefin sheets of cyclopentadiene and itsderivatives, dicyclopentadiene and its derivatives or polymers orcopolymers of cyclic diene monomers, such as norbornadiene and itsderivatives, because those sheets are excellent in weather resistanceand water resistance, are highly transparent and have high sunlighttransmittance.

[0457] The protective sheets of the solar battery modules using thefluorocarbon resin sheet or the cyclic polyolefin resin sheet utilizethe excellent properties of the fluorocarbon resin sheet or the cyclicpolyolefin resin sheet including mechanical properties, chemicalproperties and optical properties, more concretely, weather resistance,heat resistance, water resistance, light resistance, moistureresistance, soil resistance, chemical resistance and the like. Theprotective sheet is equal in optical properties, durability andprotective ability to a glass sheet commonly used as a protective sheet,has satisfactory mechanical properties including flexibility, andchemical properties, and is lighter than the glass sheet, excellent inworkability and easy to handle.

[0458] According to the present invention, the resin films or sheets maybe formed of, for example, one or some of the foregoing resins by a filmforming process, such as an extrusion process, a casting process, aT-die extrusion process, a cutting process, an inflation process or thelike, may be multilayer films or sheets of two or more kinds of theforegoing resins formed by a coextrusion process, or may be films orsheets formed by subjecting a mixture of a plurality of kinds of theforegoing resins to a film forming process. When necessary, the resinfilms or sheets may be uniaxially or biaxially oriented films or sheetsformed by subjecting resin films or sheets to a uniaxial or biaxialorientation process of a tenter system or a tubular film system.

[0459] The thickness of the resin films or sheets is in the range ofabout 12 to about 300 μm, preferably, in the range of about 20 to about200 μm.

[0460] It is desirable that the resin films or sheets of the presentinvention have a visible light transmittance of 90% or above,preferably, 95% or above and a property to transmit all incidentsunlight and to absorb the same.

[0461] When forming the resin films each of one or a plurality of theresins, various compounding ingredients and additives may be added tothe resin or resins to improve the workability, heat resistance, weatherresistance, mechanical properties, dimensional stability, oxidationresistance, slipperiness, releasability, flame retardancy, antifungalproperty, electric properties and the like. The amount of each of thecompounding ingredients and the additives is in the range of a verysmall percent to several tens percent and may optionally be determinedaccording to the purpose.

[0462] The resins may contain commonly known additives, such as alubricant, a crosslinking agent, an oxidation inhibitor, an ultravioletabsorber, a light stabilizer, a filler, a reinforcing material, astiffener, an antistatic agent, a flame retarder, a flame-resistantagent, a foaming agent, an antifungus agent, a pigment and the like. Theresins may further contain modifiers.

[0463] When necessary, a surface-treated layer 3 (FIG. 10) may be formedin a surface of each of the resin films or sheets before forming adeposited inorganic oxide film on the surface to improve adhesionbetween the resin films or sheets and a deposited inorganic oxide film.

[0464] According to the present invention, the composite resins maycontain, for example, an ultraviolet absorber and/or an oxidationinhibitor to improve the light resistance and the like. may contain, forexample, an ultraviolet absorber and/or an oxidation inhibitor toimprove the light resistance and the like.

[0465] Description will be given of the coating film of a condensationpolymer produced through the hydrolysis of a silicon compound, employedin the protective sheet in accordance with the present invention for asolar battery module and a solar battery module. When forming thecoating film, a material containing a silicon compound as a principalcomponent or a solution of the material prepared by dissolving thematerial in an appropriate solvent, such as ethanol or isopropanol, isbrought into contact with a stoichiometrically necessary amount of wateror an amount of water greater by one or several parts than thestoichiometrically necessary amount for hydrolysis to prepare acondensation polymer.

[0466] Preferably, the hydrolysis is carried out at a temperature in therange of −20 to 130° C., more preferably, in the range of 0 to 30° C. orat a temperature corresponding to the boiling point of the selectivelyused solvent.

[0467] The most proper method of bringing the material into contact withwater is dependent particularly on the reactivity of the material.

[0468] The solution of the material may be dropped at long intervalsinto a surplus amount of water or the necessary amount of water may beadded at a time or in a series of times to the solution prepared byselectively dissolving the material.

[0469] It is advantageous to introduce water into the reactive mixtureby means of an organic or an inorganic solvent containing water insteadof adding water to the reactive mixture.

[0470] It is known that the introduction of water into the reactivemixture by using a molecular sieve, and an organic solvent containingwater, such as 30% ethanol, is particularly proper for most cases.

[0471] Water can be added to the reactive mixture by using a reactionthat produces water, such as a reaction for producing an ester from anacid and an alcohol.

[0472] Suitable materials as the solvent, in addition to the effectivelower aliphatic alcohols, are ketones, preferably, lower dialkylketones, such as acetone, and methyl isobutyl ketone, esters,preferably, lower dialkyl ethers, such as diethyl ether, tetrahydrofuran(THF), amides, esters including ethyl acetate, dimethyl formamide andmixtures of the same.

[0473] Condensation polymerization by hydrolysis may selectively using acatalyst, such as a compound that discharges protons or hydroxyl ions,or an amine.

[0474] Suitable materials as the catalyst are organic or inorganicacids, such as hydrochloric acid and acetic acid, ammonia, alkalinemetal and alkaline earth hydroxides, such as organic or inorganic saltsincluding sodium hydroxide, potassium hydroxide and calcium hydroxide,and amines soluble in a reactive medium, such as lower alkylamines andalkanol amines.

[0475] Volatile acids and bases, such as ammonia and triethylamine, areparticularly preferable.

[0476] The concentration of the catalyst may be 3 mol per liter at thegreatest.

[0477] A mixture of all the source compounds need not necessarily beprepared before starting hydrolysis (condensation polymerization).Actually, in a specific case, it is advantageous to bring some of thesource compounds into contact with water in an initial stage ofhydrolysis, and then to bring the rest later into contact with water.

[0478] To reduce precipitation to the least possible extent, it ispreferable to add water in several steps, for example, in three steps.

[0479] In the first step, {fraction (1/10)} to {fraction (1/20)} of theamount of water stoichiometrically necessary for hydrolysis is added tothe source material.

[0480] After stirring a mixture of the source materials and water for ashort time, ⅕ to {fraction (1/10)} of the amount of waterstoichiometrically necessary for hydrolysis is added to the mixture, themixture is stirred for a sort time, and an amount of water is added tothe mixture so that the total amount of water added to the sourcematerial is a little greater than the stoichiometric amount.

[0481] Time necessary for condensation polymerization by hydrolysis isdependent on the source materials, the concentrations of the sourcematerials, the catalyst, reaction temperature and the like.

[0482] Generally, the reaction process for condensation polymerizationby hydrolysis is conducted at atmospheric pressure. The reaction processmay be conducted at a higher-than-atmospheric pressure or at a reducedpressure.

[0483] After all the predetermined amount of water has been added to thesource materials, it is preferable to prepare a composite materialcomprising a condensation polymer produced through the hydrolysis of asilicon compound, by stirring the mixture for a long time in the rangeof two to three hours at room temperature or at a temperature slightlyhigher than room temperature.

[0484] According to the present invention, the composite material thusprepared is applied to or printed on the surface of the depositedinorganic oxide film in a composite material film, the compositematerial film is dried and aged to form the coating film. The compositematerial film may be formed by any one of coating processes including afloating-knife coating process, a knife-over-roll coating process, aninverted knife coating process, a squeeze roll coating process, areverse roll coating process, a roll coating process, a gravure rollcoating process, a kiss-roll coating process, an air blade coatingprocess, a dip coating process, a flow coating process, a spin coatingprocess, a spray coating process, a bar coating process, a curtain-flowcoating process and the like, or any one of printing processes includinga gravure printing process, an offset printing process, a silk-screenprinting process, a transfer printing process and the like.

[0485] The desirable thickness of the coating film as dried is in therange of 0.2 to 50 g/m², more preferably, in the range of 1.0 to 25g/m².

[0486] When curing the coating film of the composite material comprisingthe condensation polymer produced through the hydrolysis of siliconoxide, by a heating means or by irradiation with ionizing radiation, itis preferable that the composite material comprising the condensationpolymer produced through the hydrolysis of silicon oxide contain aninitiator.

[0487] The initiator may be a commercially available photopolymerizationinitiator.

[0488] Possible initiators are photoreaction initiators commerciallyavailable from ciba-Geigy, Switzerland including IRUGACURE 185(1-hydroxycyclohexyl phenyl ketone), IRUGACURE 500 (1-hydroxycyclohexylphenyl ketone+benzophenone) and the like, GLOCURE 1173, 1116, 1396, 1274and 1020 commercially available from Merk, Switzerland, benzophenone,2-chlorothioxanethene, 2-methylthioxanthone, 2-isopropylthioxanthone,benzoin, 4,4-dimethoxybenzoin, benzoin ethyl ether, benzoin isopropylether, benzoin dimethyl ether, 1,1,1-trichloroacetophenone,diethoxyacetophenone and dibenzosuberon.

[0489] Particularly suitable thermal reaction initiators are diacylperoxide, peroxydicarbonate, alkylperoxy ester, dialkyl peroxide, peroxyketal, ketone peroxide and alkylperoxide organic peroxides.

[0490] Particularly preferable thermal reaction initiators are dibenzoilperoxide, perbenzoic tert-butyl and azobisisobutylonitrile.

[0491] Naturally, an ionic polymerization initiator may be used.

[0492] Particularly, a UV initiator that initiates cationicpolymerization reaction is effective with compound including R′ groupshaving epoxy groups, such as glycidyl oxypropyl trimethoxysilane, andexpressed by general formula (1).

[0493] In most cases, the result of curing by cations is moresatisfactory than that of curing by a free radical initiator under thesame conditions.

[0494] The composite material may contain an ordinary amount ofinitiator. For example, a composite substance containing 30 to 50% byweight of solid content may contain 0.5 to 2% by weight (to the totalweight) of initiator.

[0495] According to the present invention, the coating film formed byapplication or printing is cured after drying.

[0496] The coating film may be cured by a know process depending on thetype of the initiator contained therein, such as a heating process or anirradiation process using a UV lamp, a laser or the like.

[0497] It is known that a thermal curing process is particularlyadvantageous to curing a coating film including R′ groups having epoxygroups and an irradiation curing process, in most cases, is advantageousto curing a coating film containing R′ groups having unsaturated C—Cbonds.

[0498] According to the present invention, a silicon compound or siliconcompounds expressed by R′SiR₃, where R′ denotes a group stable tohydrolysis and capable of being polymerized by heat and/or ionizingradiation, and R denotes an OH group and/or a group subject tohydrolysis.

[0499] It is desirable that R′ of the general formula R′SiR₃ is an epoxyatomic group or a group including an atomic group having a C—C doublebond.

[0500] A glycidyl oxyalkyl group, particularly, a glycidyl oxyalkylgroup having an alkyl part having one to four carbon atomic groups is anexample of the group including an epoxy atomic group. Particularlypreferable group is a γ-glycidyl oxypropyl group.

[0501] Preferably, the group R′ of the general formula R′SiR₃, having anatomic group having a C—C double bond is selectively substituted alkenyland alkynyl groups, such as a straight chain, a side chain or a cyclicgroup having 2 to 20, preferably, 2 to 10 carbon atoms and at least oneC—C double bond. Particularly preferable groups as the group R′ arelower alkenyl groups, such as vinyl, 1- and 2-propenyl, butenyl,isobutenyl, phenyl vinyl and propargyl, or groups including atomicgroups including an alkynyl group, a methacryl group or an acrylicgroup.

[0502] In the general formula R′SiR₃, R is, for example, hydrogen, ahalogen, an alkoxy group, a hydroxyl group, or an alkynylcarbonyl group.

[0503] According to the present invention, particularly preferablegroups are , for example, a methoxy group, an ethoxy group, an n-propoxygroup, an i-propoxy group, a sec-butoxy group, a tert-butoxy group, anisobutoxy group, a β-methoxyethoxy group, an acetyloxy group, apropionyloxy group, a monomethylamino group, a monoethylamino group, adimethylamino group, a diethylamino group, an N-ethylanilino group, amethylcarbonyl group, an ethylcarbonyl group, a methoxycarbonyl group,an ethoxycarbonyl group and the like.

[0504] The group R of the general formula R′SIR₃ does not remain in thefinal product, is decomposed by hydrolysis, and the product ofhydrolysis must be removed immediately or later by an appropriatemethod. Therefore, a group not having any substituent and capable ofbeing hydrolyzed into a lower alcohol of a low molecular weight, such asmethanol, ethanol propanol or butanol, is particularly preferable as thegroup R. The silicon compound expressed by the general formula R′SiR₃may be used in an entirely or partly condensed form, i.e., in a compoundproduced by the partial hydrolysis of the silicon compound, individuallyor in combination with another hydrolyzable compound, such as anorganometallic compound.

[0505] Preferably, such an oligomer is a partially condensed substancesoluble in a reaction medium, having the shape of a straight or cyclicchain, a low molecular weight and a condensation degree in the range of,for example, about 2 to 100, more preferably, in the range of about 2 to6, such as polyorganosiloxane.

[0506] Specific examples of substances capable of being effectively usedas the silicon compound expressed by the general formula R′SiR₃ areγ-(meta)acryloxypropyl trimethoxysilane, vinyl trichlorosilane, vinyltrimethoxysilane, vinyl triethoxysilane, vinyltris(β-methoxyethoxy)silane and γ-glycidyl oxypropyl trimethoxysilane.

[0507] Preferably, the silicon compound expressed by the general formulaR′SiR₃ is not used individually. Preferably, the silicon compound ismixed with one or some of organometallic compounds expressed by generalformula MR_(n), where M denotes an element, such as silicon, aluminum,titanium, zirconium, vanadium, boron and tin, R denotes an OH groupand/or a easily hydrolyzable group and n denotes the valence of themetallic element, that is generally used for producing glass and ceramicmaterials, and the compounds are converted into hydrates ofcorresponding oxides by hydrolysis preferably, complete hydrolysis.

[0508] A metallic element contained in the organometallic compoundexpressed by the general formula MR_(n) is, for example, silicon,aluminum titanium, zirconium, vanadium, boron or tin. It goes withoutsaying that the present invention may use an organometallic compoundcontaining a metallic element other than those mentioned above.

[0509] In the organometallic compound expressed by the general formulaMR_(n), R may be either the same or different and may be definedsimilarly to the Rof the general formula R′SiR₃expressing the siliconcompound.

[0510] Preferably, the organometallic compound expressed by the generalformula MR_(n) and the silicon compound expressed by the general formulaR′SiR₃are used in a mixture having the molar ratio of the organometalliccompound to the silicon compound in the range of 1:99 to 99:1.

[0511] The material forming the coating film of the present inventionmay contain, in addition to the silicon compound expressed by thegeneral formula R′SiR₃ and the organometallic compound expressed by thegeneral formula MR_(n), one or some kinds of resins having hydrogen bondforming groups as a binder or binders.

[0512] Possible resins having hydrogen bond forming groups are, forexample, polymers having hydroxyl groups and their derivatives, such aspolyvinyl alcohol, polyvinyl acetal, ethylene-vinyl alcohol copolymers,phenolic resins, methylol melamine resins and their derivatives,polymers having carboxyl groups and their derivatives, such as polymersor copolymers of polymerizing unsaturated acids includingpoly(meta)acrylic acid, maleic anhydride and itaconic acid, and theiresters, such as polymers or copolymers of vinyl esters including vinylacetate, (meta)acrylic acid esters including methyl methacrylate,polymers having ether bonds, such as polyalkylene oxide, polyoxyalkyleneglycol and polyvinyl ether, silicone resins, polymers having amidebonds, such as a >N(COR) bond (R is hydrogen atom, an alkyl group whichmay have a substituent or an aryl group which may have a substituent),polyvinyl pyrrolidone having a >N(O) bond and its derivatives,polyurethane resins having urethane bonds, polymers having urea bondsand polymers having amide bonds.

[0513] According to the present invention, the resin having hydrogenbond forming groups may be used with a mixture of the silicon compoundexpressed by the general formula R′SiR₃ and the organometallic compoundexpressed by the general formula MR_(n) and the amount of the resinhaving hydrogen bond forming groups to be used is such that the weightratio of the resin having hydrogen bond forming groups to the mixture ofthe silicon compound and the organometallic compound is in the range of1:99 to 99:1, preferably, 5:30.

EXAMPLES

[0514] Examples of the third embodiment will be described hereinafter.

Example 1

[0515] (1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet)was mounted on a feed roll of a plasma chemical vapor deposition system.A 50 Å thick deposited silicon oxide thin film as a deposition-resistantprotective film was deposited on a treated surface of the polyvinylfluoride sheet treated for adhesion improvement under the followingdeposition condition.

[0516] Deposition conditions:

[0517] Reaction gas mixing ratio:Hexamethyldicyloxane:Oxygen:Helium=5:5:5 (Unit:slm)

[0518] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0519] Vacuum in deposition chamber: 3.8×10⁻² mbar

[0520] Power supplied to cooling electrode drum: 15 kW

[0521] Sheet moving speed: 100 m/min

[0522] (2) A roll of the 50 μm thick polyvinyl fluoride sheet (PVFsheet) provided with the deposition-resistant protective film wasmounted on the feed roll of a plasma chemical vapor deposition system,and a 800 Å thick deposited silicon oxide thin film was deposited on thedeposition-resistant protective film of the polyvinyl fluoride sheetunder the following deposition conditions.

[0523] Deposition conditions

[0524] Reaction gas mixing ratio:Hexamethyldicyloxane:oxygen:Helium=5:10:10 (Unit:slm)

[0525] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0526] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0527] Power supplied to cooling electrode drum: 20 kW

[0528] Sheet moving speed: 80 m/min

[0529] The 800 Å thick deposited silicon oxide film formed on thesurface of the polyvinyl fluoride sheet was subjected to a coronadischarge process to form a corona-processed surface and to increase thesurface tension of the deposited silicon oxide film from 35 dyne to 60dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

[0530] (3) Then, 25% by mole aluminum sec-butyrate was dropped at longintervals into a mixture of 45% by mole methacryl oxypropyltrimethoxysilane and 30% by mole methyl trimethoxysilane heated at roomtemperature while the mixture was stirred moderately. After all aluminumsec-butyrate had been dropped, the mixture was stirred for five minutesand was cooled to 15° C.

[0531] An amount of water equal to {fraction (1/15)} of an amount waswater necessary for complete hydrolysis was dropped into the mixturewhile the mixture was stirred.

[0532] The mixture was stirred for additional five minutes, and then wascooled to 8° C.

[0533] Hydrolysis was completed and a coating composite material wasprepared.

[0534] The coating composite material thus prepared was applied by agravure roll coating process to the corona-processed surface of thedeposited silicon oxide film formed in (2) in a coating film, thecoating film was dried at 120° C. for 1 hr to form a coating film of 1.0g/m² (dry state) in coating rate. Thus a protective sheet in accordancewith the present invention for a solar battery module was fabricated.

[0535] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the coating film of the protective sheet facinginside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0536] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 2

[0537] (1) A roll of a 50 μm thick polyvinyl fluoride film was mountedon a feed roll of a continuous vacuum evaporation system. The 50 μmthick polyvinyl fluoride film was unwound and wound around a coatingdrum. A 800 Å thick deposited aluminum oxide film was deposited on thedeposition-resistant protective film of the polyvinyl fluoride sheetunder the following conditions by a reactive evaporation process of anelectron beam (EB) heating system, in which aluminum was used as anevaporation source and oxygen gas was supplied to the continuous vacuumevaporation system.

[0538] Deposition conditions:

[0539] Evaporation source: Aluminum

[0540] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0541] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0542] EB power: 40 kW

[0543] Film moving speed: 600 m/min

[0544] Subsequently, the 800 Å thick deposited aluminum oxide filmformed on the surface of the polyvinyl fluoride sheet was processed by aglow-discharge plasma process to form a plasma-processed surface. Theglow-discharge plasma process was carried out by a glow-discharge plasmaproducing apparatus of 1500 W in plasma output immediately after thedeposition of the 800 Å thick deposited aluminum oxide film. In theglow-discharge plasma process, an oxygen/argon mixed gas of 19/1 inO₂/Ar ratio was supplied so that the pressure of the oxygen/argon mixedgas is maintained at 6×10⁻⁵ torr and the processing speed was 420m/min.

[0545] (2) A mixture of 25 g of ethyl silicate, 25 g of ethanol, 86 g of2N hydrochloric acid and 1.51 g of water was heated at 80° C. and wasstirred for 1 to 2 hr.

[0546] The molar ratio of ethyl silicate to water of the mixture was1:1:51.

[0547] Then, 2.5 g of epoxy silane (SH6040, Commercially available fromToray-Dou Corning) was added to the mixture and the mixture was stirred.

[0548] Then, 1.7 g of a 10% polyvinyl alcohol aqueous solution(polyvinyl alcohol having a polymerization degree of 2000 available fromKuraray) was added to the mixture and the mixture was stirred for 1 to 2hr. When the mixture turned transparent, 0.1 g of 32% by weightN,N-dimethylbenzylamine ethanol solution was added to prepare acomposite coating material.

[0549] The coating composite material thus prepared was applied to theplasma-processed surface of the deposited aluminum oxide film formed in(1) by a gravure roll coating process in a film of 1.0 g/m² in coatingrate to complete a protective sheet for a solar battery module.

[0550] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the coating film of the front surface protectivesheet facing inside and the surface of the 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet.Those component layers were laminated by using adhesive layers of anacrylic resin to complete a solar battery module.

[0551] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 3

[0552] (1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film)was mounted on a feed roll of a plasma chemical vapor deposition system.A 500 Å thick deposited silicon oxide thin film was deposited on one ofthe surfaces of the polyvinyl fluoride film under the followingconditions.

[0553] Deposition conditions:

[0554] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (Unit: slm)

[0555] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0556] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0557] Power supplied to cooling electrode drum: 20 kW

[0558] Film moving speed: 80 m/min

[0559] Surface for deposition: Corona-processed surface

[0560] The surface of the 500 Å thick deposited silicon oxide thin filmformed on the polyvinyl fluoride film was subjected to a coronadischarge process to form a corona-processed surface and to increase thesurface tension of the deposited silicon oxide thin film from 35 dyne to60 dyne. Corona discharge power was 10 kw and the sheet was moved at amoving speed of 100 m/min.

[0561] (2) A roll of the polyvinyl fluoride film provided with thecorona-processed deposited silicon oxide thin film was mounted on a feedroll of a continuous vacuum evaporation system. The polyvinyl fluoridefilm was unwound and wound around a coating drum and a 500 Å thickdeposited aluminum oxide thin film was deposited on the corona-processedsurface of the deposited silicon oxide thin film formed on the polyvinylfluoride film by a reactive vacuum evaporation process of an electronbeam (EB) heating system. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

[0562] Deposition conditions:

[0563] Evaporation source: Aluminum

[0564] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0565] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0566] EB power: 40 kW

[0567] Film moving speed: 600 m/min

[0568] A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 500 Å thickdeposited aluminum oxide thin film formed on the surface of thepolyvinyl fluoride sheet to a glow-discharge plasma process to form aplasma-processed surface. The glow-discharge plasma process was carriedout by a glow-discharge plasma producing apparatus of 1500 W in plasmaoutput immediately after the deposition of the 500 Å thick depositedaluminum oxide thin film. In the glow-discharge plasma process, anoxygen/argon mixed gas of 19/1 in O₂/Ar ratio was supplied so that thepressure of the oxygen/argon mixed gas is maintained at 6×10⁻⁵ torr andthe processing speed was 420 m/min.

[0569] (3) The plasma-processed surface of the deposited aluminum oxidefilm formed in (2) was coated with a film of the composite coatingmaterial prepared in Example 1. The film of the composite coatingmaterial was dried at 120° C. for 1 hr to form a coating film of 1.0g/m² (dry state) in coating rate to complete a protective sheet inaccordance with the present invention for a solar battery module.

[0570] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the coating film facing inside and the surface of the38 μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet.Those component layers were laminated by using adhesive layers of anacrylic resin to complete a solar battery module.

[0571] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE)containing an ultraviolet absorber was used instead of the 50 μm thickpolyvinyl fluoride film (PVF film) containing an ultraviolet absorber.

Example 4

[0572] (1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet)was mounted on a feed roll of a continuous vacuum evaporation system.The polyvinyl fluoride sheet was unwound and wound around a coatingdrum. A 50 Å thick deposited aluminum oxide thin film as adeposition-resistant protective film was deposited on a treated surfaceof the polyvinyl fluoride film treated for adhesion improvement by areactive vacuum evaporation process of an electron beam (EB) heatingsystem under the following conditions.

[0573] Deposition conditions:

[0574] Evaporation source: Aluminum

[0575] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0576] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0577] EB power: 20 kW

[0578] Film moving speed: 500 m/min

[0579] (2) A 800 Å thick deposited aluminum oxide film was formed by amethod similar to that of (2) of Example 2 on the deposition-resistantprotective film, i.e., the deposited aluminum oxide film, of the 50 μmthick polyvinyl fluoride sheet by a reactive vacuum evaporation processof an electron beam (EB) heating system. The surface of the depositedaluminumoxide film was subjected to a plasma process to form aplasma-processed surface.

[0580] (3) The plasma-processed surface of the deposited aluminum oxidefilm formed in (2) was coated with a film of the composite coatingmaterial prepared in Example 2 by a gravure roll coating process. Thefilm of the composite coating material was dried at 120° C. for 1 hr toform a coating film of 2.0 g/m² (dry state) in coating rate to completea protective sheet in accordance with the present invention for a solarbattery module.

[0581] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the coating film facing inside and the surface of the38 μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet.Those component layers were laminated by using adhesive layers of anacrylic resin to complete a solar battery module.

[0582] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 5

[0583] (1) Protective sheets that are the same as the protective sheetin Example 1 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the coating films of the front surface and theback surface protective sheet facing inside and with the surface of the38 μm thick polyethylene terephthalate film provided with the solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0584] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 6

[0585] (1) Protective sheets that are the same as the protective sheetin Example 2 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the coating films of the front surface and theback surface protective sheet facing inside and with the surface of the38 μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

[0586] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 7

[0587] (1) Protective sheets that are the same as the protective sheetin Example 3 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the coating films of the front surface and theback surface protective sheet facing inside and with the surface of the38 μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

[0588] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) containing anultraviolet absorber were used instead of the 50 μm thick polyvinylfluoride sheets (PVF sheets) containing the ultraviolet absorber.

Example 8

[0589] (1) Protective sheets that are the same as the protective sheetin Example 4 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the coating films of the front surface and theback surface protective sheet facing inside and with the surface of the38 μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

[0590] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheets).

Example 9

[0591] (1) A protective sheet that is the same as the protective sheetin Example 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the coating film of the back surface protectivesheet facing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the 3 mm thick glass sheet, and laminating those componentlayers by using adhesive layers of an acrylic resin.

[0592] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 10

[0593] (1) A protective sheet that is the same as the protective sheetin Example 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 0 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecoating film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 50 μm thickpolyvinyl fluoride sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0594] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 11

[0595] (1) A protective sheet that is the same as the protective sheetin Example 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecoating film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 50 μm thickpolyvinyl fluoride sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0596] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Examples 12 to 15

[0597] Front surface protective sheets in accordance with the presentinvention and solar battery modules of the same components as those ofExample 1 were fabricated by the same processes by using plastic sheetsin Examples 12 to 15 instead of the 50 μm thick polyvinyl fluoride sheet(PVF sheet).

[0598] Example 12: 100 μm thick polydicyclopentadiene resin sheet

[0599] Example 13: 100 μm thick polycarbonate resin sheet

[0600] Example 14: 100 μm thick polyacrylic resin sheet

[0601] Example 15: 100 μm thick polyethylene terephthalate resin sheet

Examples 16 to 19

[0602] Front surface protective sheets in accordance with the presentinvention and solar battery modules of the same components as those ofExample 2 were fabricated by the same processes by using plastic sheetsin Examples 16 to 19 instead of the 50 μm thick polyvinyl fluoride sheet(PVF sheet).

[0603] Example 16: 100 μm thick polydicyclopentadiene resin sheet

[0604] Example 17: 100 μm thick polycarbonate resin sheet

[0605] Example 18: 100 μm thick polyacrylic resin sheet

[0606] Example 19: 100 μm thick polyethylene terephthalate resin sheet

Example 20

[0607] (1) A 500 Å thick deposited silicon oxide film was formed on asurface of a 50 μm thick polyvinyl fluoride sheet (PVF sheet) by aradio-frequency induction heating process, in which 99.9% pure siliconmonoxide (SiO) was evaporated in a vacuum of 1×10⁻⁴ torr.

[0608] Subsequently, the surface of the 500 Å thick deposited siliconoxide film formed on the polyvinyl fluoride sheet was subjected to acorona discharge process to increase the surface tension of the samefrom 35 dyne to 60 dyne. Corona discharge power was 10 kW and the sheetwas moved at a moving speed of 100 m/min.

[0609] (2) The coating composite material prepared in Example d1 wasapplied to the corona-processed surface of the deposited silicon oxidefilm by a gravure roll coating process in a coating film, the coatingfilm was dried at 120° C. for 1 hr to form a coatinHg film of 1.0 g/m²(dry state) in coating rate. Thus a protective sheet in accordance withthe present invention for a solar battery module was fabricated.

[0610] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the coating film facing inside and the surface of the38 μm thick biaxially oriented polyethylene terephthalate film providedwith the solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0611] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-vinyl acetate copolymer containing anultraviolet absorber was instead of the 50 μm thick polyvinyl fluoridesheet (PVF sheet) containing an ultraviolet absorber.

Example 21

[0612] (1) A roll of the 50 μm thick polyvinyl fluoride sheet (PVFsheet) was mounted on the feed roll of a plasma chemical vapordeposition system, and a 800 Å thick deposited silicon oxide thin filmwas deposited on one of the surfaces of the polyvinyl fluoride sheetunder the following deposition conditions.

[0613] Deposition conditions

[0614] Reaction gas mixing ratio:Hexamethyldicyloxane:oxygen:Helium=1:10:10 (Unit: slm)

[0615] vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0616] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0617] Power supplied to cooling electrode drum: 20 kW

[0618] Sheet moving speed: 80 m/min

[0619] The 800 Å thick deposited silicon oxide film formed on thesurface of the polyvinyl fluoride sheet was subjected to a coronadischarge process to form a corona-processed surface and to increase thesurface tension of the deposited silicon oxide film from 35 dyne to 60dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

[0620] (2) The coating composite material prepared in Example 1 wasapplied by a gravure roll coating process to the corona-processedsurface of the deposited silicon oxide film in a film. The film wasdried at 120° C. for 1 hr to form a coating film of 1.0 g/m² (drystate)in coating rate. Thus a protective sheet in accordance with thepresent invention for a solar battery module was fabricated.

[0621] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the coating film of the front surface protectivesheet facing inside and the surface of the 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet.Those component layers were laminated by using adhesive layers of anacrylic resin to complete a solar battery module.

[0622] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 22

[0623] (1) A roll of a 50 μm thick polyvinyl fluoride film was mountedon a feed roll of a continuous vacuum evaporation system. The 50 μmthick polyvinyl fluoride film was unwound and wound around a coatingdrum. A 800 Å thick deposited aluminum oxide film was deposited on oneof the surfaces of the of the polyvinyl fluoride sheet under thefollowing conditions by a reactive evaporation process of an electronbeam (EB) heating system, in which aluminum was used as an evaporationsource and oxygen gas was supplied to the continuous vacuum evaporationsystem.

[0624] Deposition conditions:

[0625] Evaporation source: Aluminum

[0626] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0627] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0628] EB power: 40 kW

[0629] Film moving speed: 600 m/min

[0630] Subsequently, the 800 Å thick deposited aluminum oxide filmformed on the surface of the polyvinyl fluoride sheet was processed by aglow-discharge plasma process to form a plasma-processed surface. Theglow-discharge plasma process was carried out by a glow-discharge plasmaproducing apparatus of 1500 W in plasma output immediately after thedeposition of the 800 Å thick deposited aluminum oxide film. In theglow-discharge plasma process, an oxygen/argon mixed gas of 19/1 inO₂/Ar ratio was supplied so that the pressure of the oxygen/argon mixedgas is maintained at 6×10⁻⁵ torr and the processing speed was 420 m/min.

[0631] (2) The composite coating material prepared in Example 2 wasapplied to the plasma-processed surface of the deposited aluminum oxidefilm by a gravure roll coating process in a film. The film was dried at120° C. for 1 hr to form a coating film of 1.0 g/m² in coating rate (drystate). Thus, a protective sheet in accordance with the presentinvention for a solar battery module was fabricated.

[0632] (3) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the coating film of the front surface protectivesheet facing inside and the surface of the 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet.Those component layers were laminated by using adhesive layers of anacrylic resin to complete a solar battery module.

[0633] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Comparative Example 1

[0634] A solar battery module was fabricated by superposing a 3 mm thickglass sheet as a back surface protective sheet, a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and a 50 μm thick biaxially oriented polyethylene terephthalatefilm in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the 50 μm thick biaxially oriented polyethyleneterephthalate film, and laminating those component layers by usingadhesive layers of an acrylic resin.

Comparative Example 2

[0635] A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride sheet (PVF sheet) as a front surface protectivesheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μmthick biaxially oriented polyethylene terephthalate film provided withan array of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and a 50 μm thick biaxially orientedpolyethylene terephthalate film in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 50 μm thick polyvinyl fluoridesheet, and laminating those component layers by using adhesive layers ofan acrylic resin.

Comparative Example 3

[0636] A solar battery module was fabricated by superposing a 100 μmthick polydicyclopentadiene sheet as a front surface protective sheet, a400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and a 50 μm thick biaxially orientedpolyethylene terephthalate sheet in that order with the surface of the38 μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

Comparative Example 4

[0637] A solar battery module was fabricated by using 50 μm thickpolyvinyl fluoride sheets (PVF sheets) as a front surface protectivesheet and a back surface protective sheet. The solar battery module wasfabricated by superposing one of the 50 μm thick polyvinyl fluoridesheets (PVF sheets) as a front surface protective sheet, a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the other 50 μm thick polyvinyl fluoride sheet (PVF sheet) asa back surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

Comparative Example 5

[0638] A solar battery module was fabricated by using 100 μm thickpolydicyclopentadiene sheets as a front surface protective sheet and aback surface protective sheet. The solar battery module was fabricatedby superposing one of the 100 μm thick polydicyclopentadiene sheets as afront surface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theother 100 μm thick polydicyclopentadiene sheet in that order with thesurface of the 38 μm thick polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0639] Experiment

[0640] The protective sheets in Examples 1 to 22 of the presentinvention and those in Comparative examples 1 to 5 were subjected tototal transmittance measurement. The solar battery modules in Examples 1to 22 and Comparative examples 1 to 5 were subjected to solar batterymodule evaluation tests.

[0641] (1) Total Transmittance Measurement

[0642] Total transmittance (%) of each of the protective sheets inExamples 1 to 22 and Comparative examples 1 to 5 against the totaltransmittance of the base sheet as a reference total transmittance wasmeasured by a color computer.

[0643] (2) Solar Battery Module Evaluation Tests

[0644] The solar battery modules were subjected to environmental testsin conformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

[0645] (3) Moisture Permeability and Oxygen Permeability

[0646] The moisture permeabilities of the protective sheets in Examples1 to 22 and Comparative examples 1 to 5 were measured in an atmosphereof 40° C. and 90% RH by a moisture permeability measuring apparatus(PERMATRAN, MOCON, USA). The oxygen permeabilities of the protectivesheets in Examples 1 to 22 and Comparative examples 1 to 5 were measuredin an atmosphere of 23° C. and 90% RH by an oxygen permeabilitymeasuring apparatus (OXTRAN, MOCON, USA).

[0647] Measured data is tabulated in Table 3-1. TABLE 3-1 Total MoistureOxygen Output trans- permea- permea- reduction mittance bility bilityRatio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%) Example 1 93 0.3 0.4 3Example 2 92 0.4 0.5 2 Example 3 93 0.3 0.3 2 Example 4 90 0.4 0.6 2Example 5 92 0.4 0.4 1 Example 6 93 0.3 0.3 1 Example 7 90 0.4 0.5 1Example 8 91 0.3 0.4 1 Example 9 93 0.4 0.3 3 Example 10 91 0.1 0.4 1Example 11 91 0.1 0.3 1 Example 12 92 0.2 0.3 2 Example 13 92 0.4 0.5 3Example 14 90 0.3 0.2 2 Example 15 90 0.3 0.4 3 Example 16 92 0.1 0.2 1Example 17 91 0.4 0.4 3 Example 18 91 0.3 0.5 3 Example 19 90 0.3 0.4 2Example 20 93 0.4 0.5 3 Example 21 93 0.3 0.5 3 Example 22 93 0.4 0.5 2Comparative 89 25.0  80.0  18  Example 1 Comparative 93 27.0  28.0  15 Example 2 Comparative 92 1.1 200.0  10  Example 3 Comparative 93 27.0 28.0  12  Example 4 Comparative 93 1.0 200.0  9 Example 5

[0648] In table 3-1, moisture permeability is expressed in a unit ofg/m²/day•40° C.•100% RH, and oxygen permeability is expressed in a unitof cc/m²/day•23° C.•90% RH.

[0649] As obvious from Table 3-1, the protective sheets in Examples 1 to22 have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

[0650] Incidentally, the protective sheets in Examples 1 to 22 hadoxygen permeabilities in an atmosphere of 25° C. and 90% RH not greaterthan 2.0 cm³/m²•day•atm and moisture permeabilities in an atmosphere of40° C. and 100% RH mpy htrsyrt yjsm 3/0 g/m²•day•atm.

[0651] The output reduction ratios of the solar battery modulesemploying the protective sheets in Examples 1 to 22 were low.

[0652] The protective sheets in Comparative examples 1 to 5 had hightotal transmittances, respectively. However, the moistureimpermeabilities and the oxygen impermeabilities of the protectivesheets in Comparative examples 1 to 5 were low. Consequently, the outputreduction ratios of the solar battery modules employing the protectivesheets in Comparative examples 1 to 5 were high.

[0653] As apparent from the foregoing description, the present inventionuses a plastic sheet as abase sheet, forms a transparent, vitreousdeposited inorganic oxide thin film, such as a silicon oxide thin filmor an aluminum oxide thin film, on one of the surfaces of the plasticsheet, and fabricates a protective sheet for a solar battery module byforming a coating film of a composite material comprising a condensationpolymer produced through the hydrolysis of a silicon compound; theprotective sheet thus fabricated is used as the front surface protectivesheet or the back surface protective sheet of a solar battery module;the solar battery module is fabricated by, for example, superposing theprotective sheet as a front surface protective sheet, a filler layer, afilm provided with solar cells, i.e., photovoltaic cells, a filler layerand the protective sheet as a back surface protective sheet in thatorder in a superposed structure with the deposited inorganic oxide thinfilms facing inside, bringing the component layers of the superposedstructure into close contact by vacuum and bonding together thosecomponent layers by a lamination process using hot pressing; and theprotective sheet transmits sunlight at a high transmittance, isexcellent in strength, weather resistance, heat resistance, waterresistance, light resistance, wind endurance, hailstorm resistance,chemical resistance, moisture resistance and soil resistance, has a highimpermeability to moisture and oxygen, limits performance degradationdue to aging to the least extent, very durable, has excellent protectiveability, and can be used for the stable fabrication of a low-cost, safesolar battery module.

[0654] The materials mentioned in the description of the first and thesecond embodiment are applicable to the third embodiment.

[0655] Fourth Embodiment

[0656] The present invention will be described hereinafter withreference to the accompanying drawings.

[0657] In this description, the term “sheet” is used in its broad senseto denote both sheets and films, and the term “film” is used in itsbroad sense to denote both sheets and films.

[0658] Protective sheets in accordance with the present invention forsolar battery modules and solar battery modules employing the protectivesheets will be described with reference to the accompanying drawings.FIGS. 16, 17, 18, 19 and 20 are typical sectional views of protectivesheets in examples in a fourth embodiment according to the presentinvention for a solar battery module, and FIGS. 21, 22 and 23 aretypical sectional views of solar battery modules employing theprotective sheet shown in FIG. 16.

[0659] Referring to FIG. 16, a protective sheet A in a first example ofthe fourth embodiment of the present invention for a solar batterymodule is a laminated structure constructed by laminating at least twobasic structures each comprising a fluorocarbon resin sheet(weather-resistant sheet) I and a deposited inorganic oxide film 2formed on one of the surfaces of the fluorocarbon resin sheet 1.

[0660] A surface-treated layer 3 may be formed in the fluorocarbon resinsheet 1, and a coating film 103 of a polymer produced through thehydrolysis of a silicon compound may be formed on the depositedinorganic oxide film 2.

[0661] As shown in FIG. 17, a protective sheet A₁ in a second example ofthe fourth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising afluorocarbon resin sheet 1 and a deposited inorganic oxide thin film 2formed on one of the surfaces of the fluorocarbon resin sheet 1 by usingan adhesive layer 203.

[0662] As shown in FIG. 18 a protective sheet A₃ in a third example ofthe fourth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising afluorocarbon resin sheet 1 and a deposited inorganic oxide thin film 2formed on one of the surfaces of the fluorocarbon resin sheet 1, and aresin sheet 204 having a high strength by using adhesive layers 203 sothat the resin sheet 204 is sandwiched between the basic structures.

[0663] As shown in FIG. 19, a protective sheet A₃ in a fourth example ofthe fourth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising afluorocarbon resin sheet 1 and a multilayer film 4 comprising at leasttwo deposited inorganic oxide thin films 2 and formed on one of thesurfaces of the fluorocarbon resin sheet 1.

[0664] As shown in FIG. 20, a protective sheet A₄ in a fifth example ofthe fourth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising afluorocarbon resin sheet 1, and a composite film 5 consisting of a firstdeposited inorganic oxide thin film 2 a formed by a chemical vapordeposition process on one of the surfaces of the fluorocarbon resinssheet 1 and a second deposited inorganic oxide thin film 2 b formed of amaterial different from that of the first deposited inorganic oxide thinfilm 2 a by a physical vapor deposition process on the first depositedinorganic oxide thin film 2 a.

[0665] Those protective sheets are only examples of the protective sheetin the fourth embodiment and the present invention is not limitedthereto.

[0666] For example, when laminating at least the two basic structureseach consisting of the fluorocarbon resin sheet and the depositedinorganic oxide thin film, the basic structures may be superposed withthe respective deposited inorganic oxide thin films thereof facing eachother or with the fluorocarbon resin sheet of one of the basicstructures and the deposited inorganic oxide thin film of the otherbasic structure facing each other.

[0667] A solar battery module employing this protective sheet Aembodying the present invention and shown in FIG. 16 will be describedby way of example. Referring to FIG. 21, a solar battery module Temploys the protective sheet A shown in FIG. 16 as its front surfaceprotective sheet 11. The solar battery module T is fabricated bysuperposing the front surface protective sheet 11(A), a filler layer 12,a photovoltaic layer 13 of solar cells, a filler layer 14 and agenerally known back surface protective sheet 15 in that order in asuperposed structure, and subjecting the superposed structure to agenerally known forming process, such as a lamination process, in whichthose component layers of the superposed structure are brought intoclose contact by vacuum and are bonded together by hot pressing. Eitherof the surfaces of the front surface protective sheet 11 may faceinside.

[0668] Another solar battery module T₂ shown in FIG. 22 employs theprotective sheet A shown in FIG. 16 as its back surface protective sheet16. The solar battery module T₂ is fabricated by superposing a generallyknown front surface protective sheet 17, a filler layer 12, aphotovoltaic layer 13 of solar cells, a filler layer 14 and the backsurface protective sheet 16(A) in that order in a superposed structure,and subjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing.

[0669] A third solar battery module T₃ shown in FIG. 23 employs theprotective sheet A shown in FIG. 16 as its front surface protectivesheet 11 and its back surface protective sheet 16. The solar batterymodule T₃is fabricated by superposing the front surface protective sheet11(A), a filler layer 12, a photovoltaic layer 13 of solar cells, afiller layer 14 and the protective sheet 16(A) in that order in asuperposed structure, and subjecting the superposed structure to agenerally known forming process, such as a lamination process, in whichthose component layers of the superposed structure are brought intoclose contact by vacuum and are bonded together by hot pressing. Eitherof the surfaces of each of the protective sheets 11 and 16 may faceinside.

[0670] The foregoing protective sheets in accordance with the presentinvention and the foregoing solar battery modules employing thoseprotective sheets are examples intended to illustrate the invention andnot to be construed to limit the scope of the invention.

[0671] For example, the foregoing solar battery modules may compriseadditional layers for sunlight absorption, reinforcement or the like.

[0672] Description will be given of methods of forming the protectivesheet by laminating at least the two basic structures each comprisingthe fluorocarbon resin sheet and the deposited inorganic oxide thinfilm, and forming the solar battery module employing the protectivesheets. There are various possible methods.

[0673] A first method in accordance with the present invention uses atleast the two basic structures each comprising the fluorocarbon resinsheet 1 and the deposited inorganic oxide thin film 2, and laminates thetwo basic structures by using the adhesive layer 203.

[0674] A second method in accordance with the present invention uses atleast the two basic structures each comprising the fluorocarbon resinsheet 1 and the deposited inorganic oxide thin film 2, and laminates thetwo basic structures by using the adhesive layer 203 extrudedindividually between the two basic structures or in a coextrusion mode.

[0675] A third method in accordance with the present invention uses atleast the two basic structures each comprising the fluorocarbon resinsheet 1 and the deposited inorganic oxide thin film 2, sandwiches thehigh-strength resin sheet 204 between the two basic structures, andlaminates the component layers by using adhesive layers.

[0676] The foregoing methods of laminating at least the two basicstructures each comprising the fluorocarbon resin sheet and thedeposited inorganic oxide thin film are only examples and the presentinvention is not limited thereto.

[0677] When necessary, the surface of the deposited inorganic oxide thinfilm 2 formed on the fluorocarbon resin sheet 1 or the surface of thefluorocarbon resin sheet 1 to be bonded to another surface may beprocessed for adhesion improvement by a surface pretreatment process,such as a corona discharge process, an ozone process, a low-temperatureor atmospheric pressure plasma process, a glow-discharge process, anoxidation process using a chemical or the like.

[0678] The surface pretreatment process may be an independent process tobe carried out after forming the deposited inorganic oxide thin film.When the surface treatment process is a low-temperature plasma processor a glow discharge process, the surface pretreatment process may becarried out in an in-line processing mode in a process for forming thedeposited inorganic oxide thin film, which is effective in reducing themanufacturing cost.

[0679] The surface of the fluorocarbon resin sheet provided with thedeposited inorganic oxide thin film is finished by the surfacepretreatment process for the adhesion improvement of the same. Theimprovement of adhesion can be achieved also by forming a layer of aprimer, an undercoater, an anchoring agent or the like.

[0680] Suitable materials for forming the coating layer are, forexample, composite resins containing a polyester resin, a polyurethaneresin, an acrylic resin or the like as a principal component of avehicle.

[0681] The coating layer may be formed of a coating material of, forexample, a solvent type, an aqueous solution type or an emulsion type bya roll coating process, a gravure roll coating process, a kiss-rollcoating process or the like.

[0682] Suitable materials for forming the adhesive layer for bondingtogether the superposed layers are polyvinyl acetate adhesives,polyacrylate adhesives including homopolymers of ethyl acrylate, butylacrylate and 2-ethylhexylester acrylate, and copolymers of thosehomopolymers and methyl methacrylate, acrylonitrile or styrene,cyanoacrylate adhesives, ethylene copolymer adhesives includingcopolymers of ethylene and monomers including vinyl acetate, ethylacrylate, acrylic acid, methacrylic acid and the like, celluloseadhesives, polyester adhesives, polyamide adhesives, polyimideadhesives, amino resin adhesives including urea resins and melamineresins, phenolic resin adhesives, epoxy adhesives, polyurethaneadhesives, reactive (meta)acrylic adhesives, rubber adhesives includingstyrene-butadiene rubbers, chloroprene rubbers and nitrile rubbers,silicone adhesives, inorganic adhesive including alkaline metal silicateand low-melting glass and the like.

[0683] Those adhesives may be of any one of an aqueous type, a solutiontype, an emulsion type and dispersion type, may be of any one of formsincluding a film, a sheet, powder or a solid, and may be of any one ofbonding types including a chemical reaction type, a solventvolatilization type, a hot melt type, a hot pressing type and the like.

[0684] The adhesive may be applied to the sheet by, for example, a rollcoating process, a gravure roll coating process, a kiss-roll coatingprocess and the like or may be printed on the sheet by a printingprocess.

[0685] The fusible, extrudable adhesive resin for forming an extrudedadhesive resin layer in the laminating process may be any one or amixture of some of fusible resins including low-density polyethylenes,medium-density polyethylenes, high-density polyethylenes, linearlow-density polyethylenes, polypropylenes, ethylene-vinyl acetatecopolymers, ionomers, ethylene-ethyl acrylate copolymers,ethylene-acrylate copolymers, ethylene-methacrylic acid copolymers,ethylene-propylene copolymers, methyl pentene polymers, acid-modifiedpolyolefin resins produced by modifying polyolefin resins, such aspolyethylenes or polypropylenes, by an unsaturated carboxylic acid, suchas acrylic acid, methacrylic acid, maleic acid, maleic anhydride,fumaric acid, itaconic acid or the like, polyvinyl acetate resins,polyester resins, polystyrene resins, cyclic polyolefin resins,ethylene-α-olefin copolymers produced by polymerization using ametallocene catalyst, and the like.

[0686] The extruded adhesive resin layer is formed of one or some of theforegoing resins by an extrusion or a coextrusion process.

[0687] When laminating layers by using the extruded adhesive layer, ananchoring layer of a bonding assistant, such as an anchoring agent, maybe used to bond the layers firmly together.

[0688] Possible anchoring agents are, for example, organic titaniumcompounds, such as alkyltitanate, isocyanates, polyethylene imines,polybutadienes and the like. The anchoring agent may be eitheroil-soluble or water-soluble.

[0689] Desirably, the anchoring agent is applied by a coating process,such as a roll coating process, a gravure roll coating process, akiss-roll coating process or the like, to the layer in a coating film of0.1 to 5 g/m² (dry state) in coating rate.

[0690] The third may use a laminating adhesive for laminating thelayers.

[0691] The high-strength resin sheets to be laminated may be resin filmsor resin sheets excellent in physical and chemical strength, dimensionalstability, weather resistance, heat resistance, water resistance, lightresistance, chemical resistance, insulating property, flexibility,bending property, workability and the like. Possible films or sheets aretough films or sheets of polyester resins including ethylene-vinylacetate copolymers, polyethylene terephthalates, polybutyleneterephthalates, polyethylene naphthalates and polytetramethyleneterephthalates, polyolefin resins including polyethylenes,polypropylenes, and ethylene-propylene copolymers, polyamide resinsincluding nylon 12 and nylon 66, polyimide resins including polyimides,polyamidimides and polyetherimides, fluorocarbon resins includingpolytetrafluoroethylenes, polytrifluoroethylenes, polyvinilidenefluorides and polyvinyl fluorides, polyether sulphones, polyetherketones, polyphenylene sulfides, polyarylates, polyesterethers, aromaticpolyamides, polycarbonates, cyclic polyolefins and the like.

[0692] The resin films or sheets may be extruded or coextruded films orsheets, and may be nonoriented, uniaxially oriented or biaxiallyoriented. Desirably, the thickness of the resin films or sheets is inthe range of about 6 to 300 μm, preferably, in the range of 10 to 100μm.

[0693] When laminating sheets with a high-strength sheet sandwichedbetween the sheets, a laminating adhesive may be used in addition to oneof the foregoing adhesives.

[0694] The laminating adhesive may be any one of laminating adhesives ofa solvent type, an aqueous type or an emulsion type including single- ortwo-component, hardening or nonhardening vinyl resins, (meta)acrylicresins, polyamide resins, polyester resins, polyurethane resins, epoxyresins, phenolic resins and rubbers.

[0695] The laminating adhesive may contain an adhesion promoting agent,such as a silane coupling agent, and/or one or some of additivesincluding an ultraviolet absorber, an oxidation inhibitor, a stabilizerand the like.

[0696] Desirably, the laminating adhesive is applied by a coatingprocess, such as a roll coating process, a gravure roll coating process,a kiss-roll coating process or the like, to the sheet in a coating filmof 0.1 to 10 g/m² (dry state) in coating rate.

[0697] Particularly desirable resin sheets among the foregoinghigh-strength resin sheets are extruded or coextruded films or sheets ofone or some of ethylene-vinyl acetate copolymers, polyethylene resinsand cyclic polyolefin resins. Possible cyclic polyolefin resin films orsheets are those of, for example, cyclic diene polymers includingcyclopentadiene and its derivatives, dicyclopentadiene and itsderivatives, cyclohexadiene and its derivatives, norbornadiene and itsderivatives, or one or some transparent cyclic polyolefin resinsconsisting of one or some of copolymers of those cyclic dienes, andolefin monomers including ethylene, propylene, 4-methyl-1-pentene,styrene, butadiene and isoprene.

[0698] Transparent cyclic polyolefin resins including cyclic dienepolymers, such as cyclopentadiene and its derivatives +anddicyclopentadiene and its derivatives are particularly preferablebecause those transparent cyclic polyolefin resins are excellent inweather resistance and water resistance, is transparent and ispreferable from the viewpoint of sunlight transmission.

[0699] The front surface protective sheets in accordance with thepresent invention for solar battery modules using the cyclic polyolefinresin films or sheets utilize the excellent properties of the cyclicpolyolefin resin films or sheets including mechanical properties,optical properties, weather resistance, heat resistance, waterresistance, light resistance, moisture resistance, soil resistance,chemical resistance and the like. The front surface protective sheet isequal in optical properties and durability to a glass sheet generallyused as a protective sheet, has satisfactory mechanical properties, andis more flexible and lighter than a glass sheet, excellent inworkability and easy to handle.

[0700] It is desirable that the cyclic polyolefin resin of the presentinvention has a visible light transmittance of 90% or above, preferably,95% or above and a property to transmit all incident sunlight.

[0701] The cyclic polyolefin resin film or sheet in accordance with thepresent invention is excellent in adhesion to a deposited inorganicoxide thin film or a fluorocarbon resin sheet, a two-layer laminatedsheet formed by laminating the cyclic polyolefin resin film or sheet,and the deposited inorganic oxide thin film or the fluorocarbon resinsheet has a very high bonding strength, and the layers of the two-layerlaminated sheet does not delaminate. A two-layer barrier film consistingof a deposited inorganic oxide thin film and a cyclic polyolefin resinfilm or sheet has a high impermeability to oxygen gas and moisture,particularly to moisture. Thus, the present invention provides a verysatisfactory front surface protective sheet having excellent propertiesincluding transparency, heat resistance, hot water resistance andaptitude for lamination.

[0702] Various compounding ingredients and additives may be added to theadhesive layer, the extruded adhesive resin layer or the high-strengthresin sheet to improve the workability, heat resistance, weatherresistance, mechanical properties, dimensional stability, oxidationresistance, slipperiness, releasability, flame retardancy, antifungalproperty, electric properties and the like. The amount of each of thecompounding ingredients and the additives is in the range of a verysmall percent to several tens percent and may optionally be determinedaccording to the purpose.

[0703] Commonly known additives, such as a lubricant, a crosslinkingagent, an oxidation inhibitor, an ultraviolet absorber, a lightstabilizer, a filler, a reinforcing material, a stiffener, an antistaticagent, a flame retarder, a flame-resistant agent, a foaming agent, anantifungus agent, a pigment and the like may be used. A modifying resinmay be used.

[0704] According to the present invention, it is particularly preferableto use an ultraviolet absorber and/or an oxidation inhibitor among thoseadditives.

[0705] The ultraviolet absorber absorbs detrimental ultraviolet rayscontained in sunlight, converts the energy of ultraviolet rays intoharmless thermal energy in its molecules to prevent active species thatstarts the photodeterioration of polymers from being excited. One orsome of ultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

[0706] The oxidation inhibitor prevents the light deterioration orthermal deterioration of polymers. Suitable oxidation inhibitors are,for example, those of a phenol group, an amine group, a sulfur group, aphosphoric acid group and the like.

[0707] The ultraviolet absorber or the oxidation inhibitor may be anultraviolet absorbing polymer or an oxidation inhibiting polymerproduced by chemically bonding an ultraviolet absorber of thebenzophenone group or an oxidation inhibitor of the phenol group to theprincipal chains or the side chains of a polymer.

[0708] The ultraviolet absorber and/or the oxidation inhibitor contentis dependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

[0709] When necessary, a surface-treated layer may be formed in asurface for bonding by a surface pretreatment process for adhesionimprovement. The surface-treated layer may be formed by, for example, acorona discharge treatment, an ozone treatment, an atmospheric orlow-temperature plasma treatment using oxygen gas or nitrogen gas, aglow discharge treatment, an oxidation treatment using a chemical or thelike.

[0710] The surface pretreatment for adhesion improvement may form alayer of a primer, an undercoater, an anchoring agent or the like.

[0711] The coating layer may be formed of, for example, a compositeresin containing a polyester resin, a polyurethane resin, an acrylicresin or the like as a principal component of its vehicle.

[0712] The coating layer may be formed of a coating material of, forexample, a solvent type, an aqueous solution type or an emulsion type bya roll coating process, a gravure roll coating process, a kiss-rollcoating process or the like.

[0713] The surface pretreatment for adhesion improvement may form, asthe surface-treated layer, a nonbarrier deposited inorganic oxide thinfilm of a thickness in the range of 20 to 100 Å, preferably, in therange of 30 to 60 Å by a process similar to that for forming thedeposited inorganic oxide thin film. an emulsion type by a roll coatingprocess, a gravure roll coating process a kiss-roll coating process orthe like. The surface pretreatment for adhesion improvement may form, asthe surface-treated layer, a nonbarrier deposited inorganic oxide thinfilm of a thickness in the range of 20 to 100 Å, preferably, in therange of 30 to 60 Å by a process similar to that for forming thedeposited inorganic oxide thin film.

EXAMPLES

[0714] Examples of the fourth embodiment will be described hereinafter.

Example 1

[0715] (1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet),i.e., base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polyvinyl fluoride sheet was unwound and woundaround a coating drum and a 500 Å thick deposited aluminum oxide thinfilm was deposited on a treated surface of the polyvinyl fluoride sheettreated for adhesion improvement by a reactive vacuum evaporationprocess of an electron beam (EB) heating system to form a coatedpolyvinyl fluoride sheet. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

[0716] Deposition conditions:

[0717] Evaporation source: Aluminum

[0718] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0719] Vacuum in deposition chamber: 2.1×1⁻⁶ mbar

[0720] EB power: 40 kW

[0721] Sheet moving speed: 600 m/min

[0722] (2) The 500 Å thick deposited aluminum oxide thin film of thecoated polyvinyl fluoride sheet was subjected to a glow-discharge plasmaprocess to form a plasma-processed surface. The glow-discharge plasmaprocess was carried out by a glow-discharge plasma producing apparatusof 1500 W in plasma output immediately after the deposition of the 500 Åthick deposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

[0723] (3) A laminating adhesive layer of a two-component polyurethanelaminating adhesive was formed in 1.0 g/m² (dry state) in coating rateby a gravure roll coating process on the plasma-processed surface of thedeposited aluminum oxide film of each of two coated polyvinyl fluoridesheets similar to that formed by (1) and (2), the two coated polyvinylfluoride sheets were disposed with the laminating adhesive layersthereof facing each other, a 20 μm thick polydicyclopentadiene film wassandwiched between the coated polyvinyl fluoride sheets, and thosecomponent layers were laminated by a dry lamination process to completea protective sheet in accordance with the present invention for a solarbattery module.

[0724] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0725] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

[0726] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that a 20 μm thick polycyclopentadienefilm was used instead of the 20 μm thick polydicyclopentadiene sheet.

[0727] A fourth protective sheet in accordance with the presentinvention and a fourth solar battery module of the same components werefabricated by the same processes, except that the two coated polyvinylfluoride sheets were superposed and bonded together with the depositedaluminum oxide thin film of one of the coated polyvinyl fluoride sheetsbonded to the polyvinyl fluoride sheet of the other coated polyvinylfluoride sheet.

Example 2

[0728] (1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film),i.e., base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 500 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polyvinyl fluoride film treatedfor adhesion improvement under the following conditions to form a coatedpolyvinyl fluoride sheet.

[0729] Deposition conditions:

[0730] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (unit: slm)

[0731] Vacuum in vacuum chamber: 5.9×10⁻⁶ mbar

[0732] Vacuum in deposition chamber: 6.0×10⁻² mbar

[0733] Power supplied to cooling electrode drum: 20 kw

[0734] Film moving speed: 80 m/min

[0735] Surface for vapor deposition: Corona-processed surface

[0736] (2) The 500 Å thick deposited silicon oxide thin film of thecoated polyvinyl fluoride film was subjected to a corona dischargeprocess to form a corona-processed surface and to increase the surfacetension of the deposited silicon oxide thin film from 35 dyne to 60dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

[0737] (3) A laminating adhesive layer of 1.0 g/m² (dry state) incoating rate was formed on the corona-processed surface of the depositedsilicon oxide film of each of two coated polyvinyl fluoride sheetssimilar to that formed by (1) and (2), the two coated polyvinyl fluoridesheets were disposed with the laminating adhesive layers thereof facingeach other, a 20 μm thick polydicyclopentadiene film was sandwichedbetween the coated polyvinyl fluoride sheets, and those component layerswere laminated by a dry lamination process to complete a protectivesheet in accordance with the present invention for a solar batterymodule.

[0738] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0739] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

[0740] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that a 20 μm thick polycyclopentadienefilm was used instead of the 20 μm thick polydicyclopentadiene sheet.

[0741] A fourth protective sheet in accordance with the presentinvention and a fourth solar battery module of the same components werefabricated by the same processes, except that the two coated polyvinylfluoride sheets were superposed and bonded together with the depositedsilicon oxide thin film of one of the coated polyvinyl fluoride sheetsbonded to the polyvinyl fluoride sheet of the other coated polyvinylfluoride sheet.

Example 3

[0742] (1) A 50 μm thick polyvinyl fluoride film (PVF film) containingan ultraviolet absorber was used as a base sheet. A 500 Å thickdeposited silicon oxide thin film was deposited on a surface of thepolyvinyl fluoride film under the same conditions as those in Example 2.The surface of the deposited silicon oxide thin film was subjected to acorona discharge process to form a corona-processed surface.

[0743] (2) A 500 Å thick deposited aluminum oxide thin film wasdeposited on the corona-processed surface of the deposited silicon oxidethin film formed on the polyvinyl fluoride film under the sameconditions as those in Example 1. A coated polyvinyl fluoride film wascompleted by subjecting the surface of the deposited aluminum oxide thinfilm to a plasma process to form a plasma-processed surface therein.

[0744] (3) A laminating adhesive layer of a two-component polyurethaneadhesive containing a small amount of an ultraviolet absorber containingultrafine titanium oxide powder (particle size: 0.01 to 0.06 μm) wasformed in a coating rate of 5.0 g/m² (dry state) on the plasma-processedsurface of the deposited aluminum oxide film of each of two coatedpolyvinyl fluoride films similar to that formed by (1) and (2). The twocoated polyvinyl fluoride films were bonded together with the laminatingadhesive layers thereof in contact with each other to complete aprotective sheet in accordance with the present invention for a solarbattery module.

[0745] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet. Those component layerswere laminated by using adhesive layers of an acrylic resin to completea solar battery module.

[0746] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin film of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride film (PVF film).

[0747] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridefilms were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polyvinyl fluoride films bonded tothe polyvinyl fluoride film of the other coated polyvinyl fluoride film.

Example 4

[0748] An anchoring layer of a polyurethane anchoring agent was formedin a coating rate of 0.5 g/m² (dry state) by a gravure roll coatingprocess on the plasma-processed surface of the deposited aluminum oxidefilm of each of two coated polyvinyl fluoride sheets similar to that inExample 1. A 100 μm thick polydicyclopentadiene film was formed on theanchoring layer of each of the two coated polyvinyl fluoride sheets byan extrusion coating process. Thus a protective sheet in accordance withthe present invention for a solar battery module was completed.

[0749] A solar battery module employing the protective sheet as itsfront surface protective sheet was fabricated by the same processes asthose in Example 1.

[0750] Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

[0751] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polyvinyl fluoride sheets bonded tothe polyvinyl fluoride sheet of the other coated polyvinyl fluoridesheet.

Example 5

[0752] An anchoring layer of a polyurethane anchoring agent was formedin a coating rate of 0.5 g/m² (dry state) by a gravure roll coatingprocess on the corona-processed surface of the deposited silicon oxidefilm of each of two coated polyvinyl fluoride sheets similar to that inExample 2. A 30 μm thick polydicyclopentadiene film was formed on theanchoring layer of each of the two coated polyvinyl fluoride sheets byan extrusion coating process. Thus a protective sheet in accordance withthe present invention for a solar battery module was fabricated.

[0753] A solar battery module employing the protective sheet as itsfront surface protective sheet was fabricated by the same processes asthose in Example 2.

[0754] Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a polynorbornadiene resin was usedinstead of the polydicyclopentadiene resin.

[0755] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited siliconoxide thin film of one of the coated polyvinyl fluoride sheets bonded tothe polyvinyl fluoride sheet of the other coated polyvinyl fluoridesheet.

Example 6

[0756] A laminating adhesive layer of a two-component polyurethanelaminating adhesive containing an ultraviolet absorber containingultrafine titanium oxide powder (particle size: 0.01 to 0.06 μm) wasformed in a coating rate of 1.0 g/m² (dry state) by a gravure rollcoating process on the plasma-processed surface of the depositedaluminum oxide film of each of two coated polyvinyl fluoride sheets (PVFsheets) similar to that in Example 1. A 20 μm thickpolydicyclopentadiene film was sandwiched between the coated polyvinylfluoride sheets, and those component layers were laminated by a drylamination process to complete a protective sheet in accordance with thepresent invention for a solar battery module.

[0757] A solar battery module employing the protective sheet as itsfront surface protective sheet was fabricated by the same processes asthose in Example 1.

[0758] Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

[0759] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polyvinyl fluoride sheets bonded tothe polyvinyl fluoride sheet of the other coated polyvinyl fluoridesheet.

Example 7

[0760] (1) Protective sheets that are the same as the protective sheetin Example 1 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0761] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

[0762] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that a 20 μm thick polycyclopentadienefilm was used instead of the 20 μm thick polydicyclopentadiene film.

[0763] A fourth protective sheet in accordance with the presentinvention and a fourth solar battery module of the same components werefabricated by the same processes, except that the two coated polyvinylfluoride sheets were superposed and bonded together with the depositedaluminum oxide thin film of one of the coated polyvinyl fluoride sheetsbonded to the polyvinyl fluoride sheet of the other coated polyvinylfluoride sheet.

Example 8

[0764] (1) Protective sheets that are the same as the protective Adsheet in Example 3 were used as the front surface protective sheet andthe back surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0765] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 50 μm thick fluorocarbon resin sheetsof an ethylene-tetrafluoroethylene copolymer (ETFE) were used as thebase sheet instead of the 50 μm thick polyvinyl fluoride sheets (PVFsheet).

[0766] Third protective sheets in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that a 20 μm thick polycyclopentadienefilm was used instead of the 20 μm thick polydicyclopentadiene film.

[0767] A fourth protective sheet in accordance with the presentinvention and a fourth solar battery module of the same components werefabricated by the same processes, except that the two coated polyvinylfluoride sheets were superposed and bonded together with the depositedsilicon oxide thin film of one of the coated polyvinyl fluoride sheetsbonded to the polyvinyl fluoride sheet of the other coated polyvinylfluoride sheet.

Example 9

[0768] (1) Protective sheets that are the same as the protective sheetin Example 3 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0769] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) containing anultraviolet absorber was used instead of the 50 μm thick polyvinylfluoride sheet (PVF sheet) containing an ultraviolet absorber.

[0770] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polyvinyl fluoride sheets bonded tothe polyvinyl fluoride sheet of the other coated polyvinyl fluoridesheet.

Example 10

[0771] (1) Protective sheets that are the same as the protective sheetin Example 4 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0772] A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene resin was usedinstead of the polydicyclopentadiene resin.

[0773] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polyvinyl fluoride sheets bonded tothe polyvinyl fluoride sheet of the other coated polyvinyl fluoridesheet.

Example 11

[0774] Protective sheets that are the same as the protective sheet inExample 5 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0775] Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polynorbornadiene resin was usedinstead of the polydicyclopentadiene resin.

[0776] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited siliconoxide thin film of one of the coated polyvinyl fluoride sheets bonded tothe polyvinyl fluoride sheet of the other coated polyvinyl fluoridesheet.

Example 12

[0777] Protective sheets that are the same as the protective sheet inExample 6 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0778] Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

[0779] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polyvinyl fluoride sheets bonded tothe polyvinyl fluoride sheet of the other coated polyvinyl fluoridesheet.

Example 13

[0780] (1) A protective sheet that is the same as the protective sheetin Example 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 Vm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the 3 mm thick glass sheet, and laminating those componentlayers by using adhesive layers of an acrylic resin.

[0781] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

[0782] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that a 20 μm thick polycyclopentadienefilm was used instead of the 20 μm thick polydicyclopentadiene film.

[0783] A fourth protective sheet in accordance with the presentinvention and a fourth solar battery module of the same components werefabricated by the same processes, except that the two coated polyvinylfluoride sheets were superposed and bonded together with the depositedaluminum oxide thin film of one of the coated polyvinyl fluoride sheetsbonded to the polyvinyl fluoride sheet of the other coated polyvinylfluoride sheet.

Example 14

[0784] (1) A protective sheet that is the same as the protective sheetin Example 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thesurface of the 38 μm thick polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the 50 μm thickpolyvinyl fluoride sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

[0785] (2) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedas a base sheet instead of the 50 μm thick polyvinyl fluoride sheet (PVFsheet).

[0786] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that a 20 μm thick polycyclopentadienefilm was used instead of the 20 μm thick polydicyclopentadiene film.

[0787] A fourth protective sheet in accordance with the presentinvention and a fourth solar battery module of the same components werefabricated by the same processes, except that the two coated polyvinylfluoride sheets were superposed and bonded together with the depositedsilicon oxide thin film of one of the coated polyvinyl fluoride sheetsbonded to the polyvinyl fluoride sheet of the other coated polyvinylfluoride sheet.

Example 15

[0788] (1) A protective sheet that is the same as the protective sheetin Example 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a100 μm thick polydicyclopentadiene sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theback surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 100 μm thickpolydicyclopentadiene sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0789] (2) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer containing anultraviolet absorber(ETFE sheet) was used as a base sheet instead of the50 μm thick polyvinyl fluoride sheet (PVF sheet) containing anultraviolet absorber.

[0790] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets each provided with the deposited silicon oxide thin film and thedeposited aluminum oxide thin film were superposed and bonded togetherwith the deposited aluminum oxide thin film of one of the coatedpolyvinyl fluoride sheets bonded to the polyvinyl fluoride sheet of theother coated polyvinyl fluoride sheet.

Comparative Example 1

[0791] A solar battery module was fabricated by superposing a 100 μmthick polydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film in that order with the surfaceof the 38 μm thick polyethylene terephthalate film provided with thearray of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

Comparative Example 2

[0792] A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

Comparative Example 3

[0793] A solar battery module was fabricated by superposing a 100 μmthick polydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a back surfaceprotective sheet in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

Comparative Example 4

[0794] A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride film (PVF film), i.e., base sheet, as a frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick polyvinyl fluoride film (PVF film), i.e., base sheet, as a backsurface protective sheet in that order with the surface of the 38 μmthick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

[0795] Experiments

[0796] The protective sheets in Examples 1 to 15 of the presentinvention and those in Comparative examples 1 to 4 were subjected tototal transmittance measurement. The solar battery modules in Examples 1to 15 and Comparative examples 1 to 4 were subjected to solar batterymodule evaluation tests.

[0797] (1) Total Transmittance Measurement

[0798] Total transmittance (%) of each of the protective sheets inExamples 1 to 15 and Comparative examples 1 to 4 against the totaltransmittance of the base sheet as a reference total transmittance wasmeasured by a color computer.

[0799] (2) Solar Battery Module Evaluation Tests

[0800] The solar battery modules were subjected to environmental testsin conformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

[0801] (3) Moisture Permeability and Oxygen Permeability The moisturepermeabilities of the protective sheets in Examples 1 to 15 andComparative examples 1 to 4 were measured in an atmosphere of 40° C. and90% RH by a moisture permeability measuring apparatus (PERMATRAN, MOCON,USA). The oxygen permeabilities of the protective sheets in Examples 1to 15 and Comparative examples 1 to 5 were measured in an atmosphere of23° C. and 90% RH by an oxygen permeability measuring apparatus (OXTRAN,MOCON, USA).

[0802] Measured data is tabulated in Table 4-1. TABLE 4-1 Total MoistureOxygen Output trans- permea- permea- reduction mittance bility bilityRatio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%) Example 1 91 0.2 0.4 2Example 2 90 0.3 0.4 3 Example 3 92 0.1 0.2 1 Example 4 93 0.3 0.6 3Example 5 92 0.4 0.5 1 Example 6 90 0.2 0.4 3 Example 7 91 0.2 0.3 2Example 8 91 0.3 0.4 2 Example 9 92 0.1 0.1 1 Example 10 92 0.3 0.5 2Example 11 91 0.2 0.3 2 Example 12 90 0.1 0.1 1 Example 13 93 0.3 0.2 2Example 14 92 0.4 0.2 3 Example 15 91 0.2 0.3 3 Comparative 93 1.2200.0  10  Example 1 Comparative 93 26.7  27.5  15  Example 2Comparative 93 1.2 200.0  8 Example 3 Comparative 93 26.0  28.0  11 Example 4

[0803] In table 4-1, moisture permeability is expressed in a unit ofg/m²/day•40° C.•100% RH, and oxygen permeability is expressed in a unitof cc/m²/day•23° C.•90% RH.

[0804] As obvious from Table 4-1, the protective sheets in Examples 1 to15 have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

[0805] The output reduction ratios of the solar battery modulesemploying the protective sheets in Examples 1 to 15 were low.

[0806] The protective sheets in Comparative examples 1 to 4 had hightotal transmittances, respectively. However, the moistureimpermeabilities and the oxygen impermeabilities of the protectivesheets in Comparative examples 1 to 4 were low. Consequently, the outputreduction ratios of the solar battery modules employing the protectivesheets in Comparative examples 1 to 4 were high.

[0807] As apparent from the foregoing description, the present inventionuses a fluorocarbon resin sheet as a base sheet, fabricates a coatedfluorocarbon resin sheet by forming a transparent, vitreous depositedinorganic oxide thin film, such as a silicon oxide thin film or analuminum oxide thin film, on one of the surfaces of the fluorocarbonresin sheet, and fabricates a protective sheet for a solar batterymodule by laminating at least two coated fluorocarbon resin sheetssimilar to the foregoing coated fluorocarbon resin sheet by an adhesivelayer or the like, uses the protective sheet as the front surfaceprotective sheet or the back surface protective sheet of a solar batterymodule; fabricates a solar battery module by, for example, superposingthe protective sheet as a front surface protective sheet, a fillerlayer, a film provided with solar cells, i.e., photovoltaic cells, afiller layer and an ordinary back surface protective sheet in that orderin a superposed structure, bringing the component layers of thesuperposed structure into close contact by vacuum and bonding togetherthose component layers by a lamination process using hot pressing; andthe protective sheet transmits sunlight at a high transmittance, isexcellent in strength, weather resistance, heat resistance, waterresistance, light resistance, wind endurance, hailstorm resistance,chemical resistance, moisture resistance and soil resistance, has a highimpermeability to moisture and oxygen, limits performance degradationdue to aging to the least extent, very durable, has excellent protectiveability, and can be used for the stable fabrication of a low-cost, safesolar battery module.

[0808] The materials mentioned in the description of the first, thesecond and the third embodiment are applicable to the fourth embodiment.

[0809] Fifth Embodiment

[0810] The present invention will be described hereinafter withreference to FIGS. 16 to 23 previously used in the description of thefourth embodiment.

[0811] In this description, the term “sheet” is used in its broad senseto denote both sheets and films, and the term “film” is used in itsbroad sense to denote both sheets and films.

[0812] Referring to FIG. 16, a protective sheet A in a first example ofthe fifth embodiment of the present invention for a solar battery moduleis a laminated structure constructed by laminating at least two basicstructures each comprising a cyclic polyolefin sheet(weather-resistantsheet) 1 and a deposited inorganic oxide film 2 formed on one of thesurfaces of the cyclic polyolefin sheet 1.

[0813] A surface-treated layer 3 may be formed in the cyclic polyolefinsheet 1, and a coating film 103 of a polymer produced through thehydrolysis of a silicon compound may be formed on the depositedinorganic oxide film 2.

[0814] As shown in FIG. 17, a protective sheet A₁ in a second example ofthe fifth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising acyclic polyolefin sheet 1 and a deposited inorganic oxide thin film 2formed on one of the surfaces of the cyclic polyolefin sheet 1 by usingan adhesive layer 203.

[0815] As shown in FIG. 18 a protective sheet A₃ in a third example ofthe fourth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising acyclic polyolefin sheet 1 and a deposited inorganic oxide thin film 2formed on one of the surfaces of the fluorocarbon resin sheet 1, and aresin sheet 204 having a high strength by using adhesive layers 203 sothat the resin sheet 204 is sandwiched between the basic structures.

[0816] As shown in FIG. 19, a protective sheet A₃ in a fourth example ofthe fifth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising acyclic polyolefin 1 and a multilayer film 4 comprising at least twodeposited inorganic oxide thin films 2 and formed on one of the surfacesof the fluorocarbon resin sheet 1.

[0817] As shown in FIG. 20, a protective sheet A₄ in a fifth example ofthe fourth embodiment for a solar battery module is a laminated sheetformed by laminating at least two basic structures each comprising acyclic polyolefin sheet 1, and a composite film 5 consisting of a firstdeposited inorganic oxide thin film 2 a formed by a chemical vapordeposition process on one of the surfaces of the cyclic polyolefin sheet1 and a second deposited inorganic oxide thin film 2 b formed of amaterial different from that of the first deposited inorganic oxide thinfilm 2 a by a physical vapor deposition process on the first depositedinorganic oxide thin film 2 a.

[0818] Those protective sheets are only examples of the protective sheetin the fourth embodiment and the present invention is not limitedthereto.

[0819] For example, when laminating at least the two basic structureseach consisting of the cyclic polyolefin sheet and the depositedinorganic oxide thin film, the basic structures may be superposed withthe respective deposited inorganic oxide thin films thereof facing eachother or with the cyclic polyolefin sheet of one of the basic structuresand the deposited inorganic oxide thin film of the other basic structurefacing each other.

[0820] A solar battery module employing this protective sheet Aembodying the present invention and shown in FIG. 16 will be describedby way of example. Referring to FIG. 21, a solar battery module Temploys the protective sheet A shown in FIG. 16 as its front surfaceprotective sheet 11. The solar battery module T is fabricated bysuperposing the front surface protective sheet 11(A), a filler layer 12,a photovoltaic layer 13 of solar cells, a filler layer 14 and agenerally known back surface protective sheet 15 in that order in asuperposed structure, and subjecting the superposed structure to agenerally known forming process, such as a lamination process, in whichthose component layers of the superposed structure are brought intoclose contact by vacuum and are bonded together by hot pressing. Eitherof the surfaces of the front surface protective sheet 11 may faceinside.

[0821] Another solar battery module T₂ shown in FIG. 22 employs theprotective sheet A shown in FIG. 16 as its back surface protective sheet16. The solar battery module T₂ is fabricated by superposing a generallyknown front surface protective sheet 17, a filler layer 12, aphotovoltaic layer 13 of solar cells, a filler layer 14 and the backsurface protective sheet 16(A) in that order in a superposed structure,and subjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing.

[0822] A third solar battery module T₃ shown in FIG. 23 employs theprotective sheet A shown in FIG. 16 as its front surface protectivesheet 11 and its back surface protective sheet 16. The solar batterymodule T₃ is fabricated by superposing the front surface protectivesheet 11(A), a filler layer 12, a photovoltaic layer 13 of solar cells,a filler layer 14 and the protective sheet 16(A) in that order in asuperposed structure, and subjecting the superposed structure to agenerally known forming process, such as a lamination process, in whichthose component layers of the superposed structure are brought intoclose contact by vacuum and are bonded together by hot pressing. Eitherof the surfaces of each of the protective sheets 11 and 16 may faceinside.

[0823] The foregoing protective sheets in accordance with the presentinvention and the foregoing solar battery modules employing thoseprotective sheets are examples intended to illustrate the invention andnot to be construed to limit the scope of the invention.

[0824] For example, solar battery modules of different forms can befabricated by using the protective sheets shown in FIGS. 17 to 20, andthe foregoing solar battery modules may comprise additional layers forsunlight absorption, reinforcement or the like.

[0825] Description will be given of methods of forming the protectivesheet by laminating at least the two basic structures each comprisingthe cyclic polyolefin sheet and the deposited inorganic oxide thin film,and forming the solar battery module employing the protective sheets.There are various possible methods.

[0826] A first method in accordance with the present invention uses atleast the two basic structures each comprising the cyclic polyolefinsheet 1 and the deposited inorganic oxide thin film 2, and laminates thetwo basic structures by using the adhesive layer 203.

[0827] A second method in accordance with the present invention uses atleast the two basic structures each comprising the cyclic polyolefinsheet 1 and the deposited inorganic oxide thin film 2, and laminates thetwo basic structures by using the adhesive layer 203 extrudedindividually between the two basic structures or in a coextrusion mode.

[0828] A third method in accordance with the present invention uses atleast the two basic structures each comprising the cyclic polyolefinsheet 1 and the deposited inorganic oxide thin film 2, sandwiches thehigh-strength resin sheet 204 between the two basic structures, andlaminates the component layers by using adhesive layers 203.

[0829] The foregoing methods of laminating at least the two basicstructures each comprising the cyclic polyolefin sheet and the depositedinorganic oxide thin film are only examples and the present invention isnot limited thereto.

[0830] When necessary, the surface of the deposited inorganic oxide thinfilm 2 formed on the cyclic polyolefin sheet 1 or the surface of thecyclic polyolefin sheet 1 to be bonded to another surface may beprocessed for adhesion improvement by a surface pretreatment process,such as a corona discharge process, an ozone process, a low-temperatureor atmospheric pressure plasma process, a glow-discharge process, anoxidation process using a chemical or the like.

[0831] The surface pretreatment process may be an independent process tobe carried out after forming the deposited inorganic oxide thin film.When the surface treatment process is a low-temperature plasma processor a glow discharge process, the surface pretreatment process may becarried out in an in-line processing mode in a process for forming thedeposited inorganic oxide thin film, which is effective in reducing themanufacturing cost.

[0832] The surface of the cyclic polyolefin sheet provided with thedeposited inorganic oxide thin film is finished by the surfacepretreatment process for the adhesion improvement of the same. Theimprovement of adhesion can be achieved also by forming a layer of aprimer, an undercoater, an anchoring agent or the like, for example, onthe surface of the deposited inorganic oxide thin film or the surface ofthe cyclic polyolefin sheet.

[0833] Suitable materials for forming the coating layer are, forexample, composite resins containing a polyester resin, a polyurethaneresin, an acrylic resin or the like as a principal component of avehicle.

[0834] The coating layer may be formed of a coating material of, forexample, a solvent type, an aqueous solution type or an emulsion type bya roll coating process, a gravure roll coating process, a kiss-rollcoating process or the like.

[0835] Methods of fabricating solar battery modules from those materialswill be described. A known method uses the protective sheet inaccordance with the present invention for a solar battery module as thefront surface protective sheet or the back surface protective sheet ofthe solar battery module. The method fabricates a solar battery moduleby superposing the protective sheet as a front surface protective sheet,a filler layer, a photovoltaic layer of solar cells, a filler layer, andan ordinary protective sheet or the protective sheet in accordance withthe present invention as a back surface protective sheet in that orderin a superposed structure, when necessary, interposes layers of othermaterials between the component layers of the superposed structure,bringing the component layers of the superposed structure into closecontact by vacuum and bonding together those component layers by alamination process using hot pressing.

[0836] When necessary, and adhesive, such as a fusible adhesive, asolvent adhesive or a photocurable adhesive, containing, as a principalcomponent of its vehicle, a (meta)acrylic resin, an olefin resin, avinyl resin or the like may be used to enhance adhesion between thelayers.

[0837] When necessary, the surface to which the filler layer is to bebonded, such as the surface of the deposited inorganic oxide thin filmof the front or the back surface protective sheet of the solar batterymodule or the surface of the cyclic polyolefin sheet, may be treated bya pretreatment process, such as a corona discharge process, ozoneprocess, a low-temperature or atmospheric plasma process, aglow-discharge process, an oxidation process using a chemical or thelike, before laminating the filler layer or the like to one of thesurfaces of the front or the back surface protective sheet of the solarbattery module to enhance adhesion between the contiguous layers.

[0838] The surface pretreatment for adhesion improvement can be achievedalso by forming a coating layer of coating material, such as a primer,an undercoater, an anchoring agent or the like, on the surface of thedeposited inorganic oxide thin film or the surface of the fluorocarbonresin sheet.

[0839] The coating material may be a composite resin containing apolyester resin, a polyurethane resin, an acrylic resin or the like as aprincipal component of a vehicle.

[0840] The coating layer may be formed of a solvent coating material, anaqueous coating material or an emulsion coating material by a coatingprocess, such as a roll coating process, a gravure roll coating processor a kiss-roll coating process.

[0841] The surface pretreatment for adhesion improvement can be achievedby forming a nonbarrier deposited inorganic oxide thin film of athickness in the range of about 20 to 100 Å, preferably, in the range of30 to 60 Å as a surface-pretreated layer by the foregoing method offorming the deposited inorganic oxide film on the surface contiguouswith the filler layer, i.e., the surface of the cyclic polyolefin sheetor the deposited inorganic oxide thin film.

EXAMPLES

[0842] Examples of the fifth embodiment will be described hereinafter.

Example 1

[0843] (1) A roll of a 100 μm thick polydicyclopentadiene sheet, i.e.,base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polydicyclopentadiene sheet was unwound andwound around a coating drum and a 500 Å thick deposited aluminum oxidethin film was deposited on a treated surface of thepolydicyclopentadiene sheet treated for adhesion improvement by areactive vacuum evaporation process of an electron beam (EB) heatingsystem to form a coated polydicyclopentadiene sheet. Aluminum was usedas an evaporation source and oxygen gas was supplied to the continuousvacuum evaporation system.

[0844] Deposition conditions:

[0845] Evaporation source: Aluminum

[0846] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0847] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0848] EB power: 40 kW

[0849] Sheet moving speed: 600 m/min

[0850] (2) The 500 Å thick deposited aluminum oxide thin film of thecoated polydicyclopentadiene sheet was subjected to a glow-dischargeplasma process to form a plasma-processed surface. The glow-dischargeplasma process was carried out by a glow-discharge plasma producingapparatus of 1500 W in plasma output immediately after the deposition ofthe 500 Å thick deposited aluminum oxide thin film. In theglow-discharge plasma process, an oxygen/argon mixed gas of 19/1 inO₂/Ar ratio was supplied so that the pressure of the oxygen/argon mixedgas is maintained at 6×10⁻⁵ torr and the processing speed was 420 m/min.

[0851] (3) A laminating adhesive layer of a polyurethane laminatingadhesive consisting of a polyesterpolyol resin containing 5% by weightof benzotriazole ultraviolet absorber, and a diisocyanate compound wasformed in 1.0 g/m² (dry state) in coating rate by a gravure roll coatingprocess on the plasma-processed surface of the deposited aluminum oxidefilm of one of two coated polydicyclopentadiene sheets similar to thatformed by (1) and (2). The two coated polydicyclopentadiene sheets weredisposed with the laminating adhesive layer of one of the coatedpolydicyclopentadiene sheet and the plasma-processed surface of thedeposited aluminum oxide thin film of the other coatedpolydicyclopentadiene sheet, and the two coated polydicyclopentadienesheets were laminated by a dry lamination process to form a protectivesheet for a solar battery module.

[0852] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0853] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene sheet was used instead of the 100 μm thickpolydicyclopentadiene sheet.

[0854] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 2

[0855] (1) A roll of a 100 μm thick polydicyclopentadiene sheet, i.e.,base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 500 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polydicyclopentadiene sheettreated for adhesion improvement under the following conditions to forma coated polydicyclopentadiene sheet.

[0856] Deposition conditions:

[0857] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (Unit: slm)

[0858] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0859] vacuum in deposition chamber: 6.0×10⁻² mbar

[0860] Power supplied to cooling electrode drum: 20 kW

[0861] Film moving speed: 80 m/min

[0862] Surface for vapor deposition: Corona-processed surface

[0863] (2) The 500 Å thick deposited silicon oxide thin film of thecoated polydicyclopentadiene sheet was subjected to a corona dischargeprocess to form a corona-processed surface and to increase the surfacetension of the deposited silicon oxide thin film from 35 dyne to 60dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

[0864] (3) A laminating adhesive layer of 1.0 g/m² (dry state) incoating rate of a polyurethane laminating adhesive consisting of apolyesterpolyol resin containing 1.5% by weight of a benzotriazoleultraviolet absorber and 1.t % by weight of a hindered aminephotostabilizer, and a diisocyanate compound was formed on thecorona-processed surface of the deposited silicon oxide film of one oftwo coated polydicyclopentadiene sheets similar to that formed by (1)and (2), the two coated polydicyclopentadiene sheets were disposed withthe laminating adhesive layer of one of the two coatedpolydicyclopentadiene sheets facing the corona-processed surface of theother coated polydicyclopentadiene sheet, and the two coatedpolydicyclopentadiene sheets were laminated by a dry lamination processto form a protective sheet in accordance with the present invention fora solar battery module.

[0865] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0866] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene was used instead of the 100 μm thickpolydicyclopentadiene sheet.

[0867] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited siliconoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 3

[0868] (1) A 100 μm thick polydicyclopentadiene sheet containing anultraviolet absorber was used as a base sheet. A 500 Å thick depositedsilicon oxide thin film was deposited on a surface of thepolydicyclopentadiene sheet under the same conditions as those inExample 2. The surface of the deposited silicon oxide thin film wassubjected to a corona discharge process to form a corona-processedsurface.

[0869] (2) A 500 Å thick deposited aluminum oxide thin film wasdeposited on the corona-processed surface of the deposited silicon oxidethin film formed on the polydicyclopentadiene sheet under the sameconditions as those in Example 1. A coated polyvinyl fluoride film wascompleted by subjecting the surface of the deposited aluminum oxide thinfilm to a plasma process to form a plasma-processed surface therein.

[0870] (3) A laminating adhesive layer of a polyurethane laminatingadhesive consisting of a polyesterpolyol resin containing a small amountof an ultraviolet absorber containing ultrafine titanium oxide powder(particle size: 0.01 to 0.06 μm), and a diisocyanate compound was formedin a coating rate of 5.0 g/m² (dry state) on the plasma-processedsurface of the deposited aluminum oxide film of each of two coatedpolydicyclopentadiene sheets similar to that formed by (1) and (2)by agravure roll coating process. The two coated polydicyclopentadienesheets were bonded together with the laminating adhesive layers thereofin contact with each other to complete a protective sheet in accordancewith the present invention for a solar battery module.

[0871] (4) A solar battery module was fabricated by using the protectivesheet thus fabricated as a front surface protective sheet. The frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet. Those component layerswere laminated by using adhesive layers of an acrylic resin to completea solar battery module.

[0872] (5) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene sheet was used instead of the 100 μm thickpolydicyclopentadiene sheet.

[0873] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 4

[0874] An anchoring layer of a polyurethane anchoring agent was formedin a coating rate of 0.5 g/m² (dry state) by a gravure roll coatingprocess on the plasma-processed surface of the deposited aluminum oxidefilm of each of two coated polydicyclopentadiene sheets similar to thatin Example 1. A 30 μm thick polydicyclopentadiene film was formed on theanchoring layer of each of the two coated polydicyclopentadiene sheetsby an extrusion coating process. Thus a protective sheet in accordancewith the present invention for a solar battery module was completed.

[0875] A solar battery module employing the protective sheet as itsfront surface protective sheet was fabricated by the same processes asthose in Example 1.

[0876] Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

[0877] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 5

[0878] An anchoring layer of a polyurethane anchoring agent was formedin a coating rate of 0.5 g/m² (dry state) by a gravure roll coatingprocess on the corona-processed surface of the deposited silicon oxidefilm of each of two coated polydicyclopentadiene sheets similar to thatin Example 2. A 30 μm thick polydicyclopentadiene film was formed on theanchoring layer of each of the two coated polydicyclopentadiene sheetsby an extrusion coating process. Thus a protective sheet in accordancewith the present invention for a solar battery module was fabricated.

[0879] A solar battery module employing the protective sheet as itsfront surface protective sheet was fabricated by the same processes asthose in Example 2.

[0880] Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a polynorbornadiene resin was usedinstead of the polydicyclopentadiene resin.

[0881] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited siliconoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 6

[0882] A laminating adhesive layer of a two-component polyurethanelaminating adhesive containing a small amount of an ultraviolet absorbercontaining ultrafine titanium oxide powder (particle size: 0.01 to 0.06μm) was formed in a coating rate of 1.0 g/m² (dry state) by a gravureroll coating process on the plasma-processed surface of the depositedaluminum oxide film of each of two coated polydicyclopentadiene sheetssimilar to that in Example 1. A 20 μm thick polydicyclopentadiene filmwas sandwiched between the laminating adhesive layers of the coatedpolydicyclopentadiene sheets, and those component layers were laminatedby a dry lamination process to complete a protective sheet in accordancewith the present invention for a solar battery module.

[0883] A solar battery module employing the protective sheet wasfabricated by the same processes as those in Example 1.

[0884] Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

[0885] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 7

[0886] (1) Protective sheets that are the same as the protective sheetin Example 1 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0887] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 100 μm thick polycyclopentadienesheets were used instead of the 100 μm thick polydicyclopentadienesheets.

[0888] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 8

[0889] (1) Protective sheets that are the same as the protective sheetin Example 2 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0890] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 100 μm thick polycyclopentadienesheets were used as the base sheets instead of the 100 μm thickpolydicyclopentadiene sheets.

[0891] Third protective sheets in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited siliconoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 9

[0892] (1) Protective sheets that are the same as the protective sheetin Example 3 were used as the front surface protective sheet and theback surface protective sheet of a solar battery module. The solarbattery module was fabricated by superposing the front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

[0893] (2) Protective sheets in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadienesheet) containing an ultraviolet absorber was used instead of the 100 μmthick polydicyclopentadiene sheet containing an ultraviolet absorber.

[0894] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polyvinyl fluoridesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 10

[0895] Protective sheets that are the same as the protective sheet inExample 4 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0896] A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene resin was usedinstead of the polydicyclopentadiene resin.

[0897] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 11

[0898] Protective sheets that are the same as the protective sheet inExample 5 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0899] Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene resin was usedinstead of the polydicyclopentadiene resin.

[0900] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited siliconoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 12

[0901] Protective sheets that are the same as the protective sheet inExample 6 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0902] Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

[0903] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 13

[0904] (1) A protective sheet that is the same as the protective sheetin Example 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the 3 mm thick glass sheet, and laminating those componentlayers by using adhesive layers of an acrylic resin.

[0905] (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadienewas used instead of the 100 μm thick polydicyclopentadiene sheet.

[0906] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited aluminumoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 14

[0907] (1) A protective sheet that is the same as the protective sheetin Example 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick fluorocarbon resin sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theback surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 50 μm thick fluorocarbon resinsheet, and laminating those component layers by using adhesive layers ofan acrylic resin.

[0908] (2) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene sheet was used as a base sheet instead of the 100 μmthick polydicyclopentadiene sheet.

[0909] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets were superposed and bonded together with the deposited siliconoxide thin film of one of the coated polydicyclopentadiene sheets bondedto the polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 15

[0910] (1) A protective sheet that is the same as the protective sheetin Example 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a100 μm thick polydicyclopentadiene sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theback surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 100 μm thickpolydicyclopentadiene sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0911] (2) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 100 μm thickpolycyclopentadiene sheet containing an ultraviolet absorber () was usedas a base sheet instead of the 100 μm thick polydicyclopentadiene sheetcontaining an ultraviolet absorber.

[0912] A third protective sheet in accordance with the present inventionand a third solar battery module of the same components were fabricatedby the same processes, except that the two coated polydicyclopentadienesheets each provided with the deposited silicon oxide thin film and thedeposited aluminum oxide thin film were superposed and bonded togetherwith the deposited aluminum oxide thin film of one of the coatedpolydicyclopentadiene sheets bonded to the polydicyclopentadiene sheetof the other coated polydicyclopentadiene sheet.

Comparative Example 1

[0913] A solar battery module was fabricated by superposing a 100 μmthick polydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film in that order with the surfaceof the 38 μm thick polyethylene terephthalate film provided with thearray of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

Comparative Example 2

[0914] A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

Comparative Example 3

[0915] A solar battery module was fabricated by superposing a 100 μmthick polydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a back surfaceprotective sheet in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

Comparative Example 4

[0916] A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride film (PVF film), i.e., base sheet, as a frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick polyvinyl fluoride film (PVF film), i.e., base sheet, as a backsurface protective sheet in that order with the surface of the 38 μmthick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

[0917] Experiments

[0918] The protective sheets in Examples 1 to 15 of the presentinvention and those in Comparative examples 1 to 4 were subjected tototal transmittance measurement. The solar battery modules in Examples 1to 15 and Comparative examples 1 to 4 were subjected to solar batterymodule evaluation tests.

[0919] (1) Total Transmittance Measurement

[0920] Total transmittance (%) of each of the protective sheets inExamples 1 to 15 and Comparative examples 1 to 4 against the totaltransmittance of the base sheet as a reference total transmittance wasmeasured by a color computer.

[0921] (2) Solar Battery Module Evaluation Tests

[0922] The solar battery modules were subjected to environmental testsin conformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

[0923] (3) Moisture Permeability and Oxygen Permeability The moisturepermeabilities of the protective sheets in Examples 1 to 15 andComparative examples 1 to 4 were measured in an atmosphere of 40° C. and90% RH by a moisture permeability measuring apparatus (PERMATRAN, MOCON,USA). The oxygen permeabilities of the protective sheets in Examples 1to 22 and Comparative examples 1 to 5 were measured in an atmosphere of23° C. and 90% RH by an oxygen permeability measuring apparatus (OXTRAN,MOCON, USA).

[0924] Measured data is tabulated in Table 5-1. TABLE 5-1 Total MoistureOxygen Output trans- permea- permea- reduction mittance bility bilityRatio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%) Example 1 92 0.2 0.4 2Example 2 91 0.3 0.4 3 Example 3 90 0.1 0.2 1 Example 4 93 0.3 0.6 3Example 5 91 0.4 0.5 1 Example 6 92 0.2 0.4 3 Example 7 92 0.2 0.4 1Example 8 91 0.3 0.4 2 Example 9 90 0.1 0.2 1 Example 10 93 0.3 0.6 2Example 11 92 0.4 0.5 1 Example 12 92 0.2 0.4 1 Example 13 92 0.2 0.4 5Example 14 91 0.3 0.4 4 Example 15 90 0.1 0.2 3 Comparative 92 1.2200.0  10  Example 1 Comparative 93 26.3  27.2  15  Example 2Comparative 92 1.2 200.0  8 Example 3 Comparative 93 26.3  27.2  11 Example 4

[0925] In table 5-1, moisture permeability is expressed in a unit ofg/m²/day•40° C.•100% RH, and oxygen permeability is expressed in a unitof cc/m²/day•23° C.•90% RH.

[0926] As obvious from Table 5-1, the protective sheets in Examples 1 to15 have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

[0927] The output reduction ratios of the solar battery modulesemploying the protective sheets in Examples 1 to 15 were low.

[0928] The protective sheets in Comparative examples 1 to 4 had hightotal transmittances, respectively. However, the moistureimpermeabilities and the oxygen impermeabilities of the protectivesheets in Comparative examples 1 to 4 were low. Consequently, the outputreduction ratios of the solar battery modules employing the protectivesheets in Comparative examples 1 to 4 were high.

[0929] As apparent from the foregoing description, the present inventionuses a cyclic polyolefin sheet as a base sheet, fabricates a coatedfluorocarbon resin sheet by forming a transparent, vitreous depositedinorganic oxide thin film, such as a silicon oxide thin film or analuminum oxide thin film, on one of the surfaces of the cyclicpolyolefin sheet, and fabricates a protective sheet for a solar batterymodule by laminating at least two coated cyclic polyolefin sheetssimilar to the foregoing coated cyclic polyolefin sheet by an adhesivelayer or the like, uses the protective sheet as the front surfaceprotective sheet or the back surface protective sheet of a solar batterymodule; fabricates a solar battery module by, for example, superposingthe protective sheet as a front surface protective sheet, a fillerlayer, a film provided with solar cells, i.e., photovoltaic cells, afiller layer and the protective sheet as a back surface protective sheetin that order in a superposed structure, bringing the component layersof the superposed structure into close contact by vacuum and bondingtogether those component layers by a lamination process using hotpressing; and the protective sheet transmits sunlight at a hightransmittance, is excellent in strength, weather resistance, heatresistance, water resistance, light resistance, wind endurance,hailstorm resistance, chemical resistance, moisture resistance and soilresistance, has a high impermeability to moisture and oxygen, limitsperformance degradation due to aging to the least extent, very durable,has excellent protective ability, and can be used for the stablefabrication of a low-cost, safe solar battery module.

[0930] The materials mentioned in the description of the first to thefourth embodiment are applicable to the fifth embodiment. by alamination process using hot pressing; and the protective sheettransmits sunlight at a high transmittance, is excellent in strength,weather resistance, heat resistance, water resistance, light resistance,wind endurance, hailstorm resistance, chemical resistance, moistureresistance and soil resistance, has a high impermeability to moistureand oxygen, limits performance degradation due to aging to the leastextent, very durable, has excellent protective ability, and can be usedfor the stable fabrication of a low-cost, safe solar battery module.

[0931] The materials mentioned in the description of the first to thefourth embodiment are applicable to the fifth embodiment.

[0932] Sixth Embodiment

[0933] The present invention will be described hereinafter withreference to the accompanying drawings.

[0934] FIGS. 24 to 28 are typical sectional views of protective sheetsin accordance with the present invention for solar battery modules, andFIG. 29 is a typical sectional view of a solar battery module employinga protective sheet shown in FIG. 24.

[0935] Referring to FIG. 24, a front surface protective sheet A in afirst example of the sixth embodiment of the present invention for asolar battery module comprises a fluorocarbon resin sheet(weather-resistant sheet) 1 and deposited inorganic oxide film 2deposited on one of the surfaces of the fluorocarbon resin sheet 1. Asoil resistant layer 303 and/or an ultraviolet absorbing layer 304 isformed on one of the surfaces of the fluorocarbon resin sheet 1.

[0936] Referring to FIG. 25, a front surface protective sheet A₁ in asecond example of the sixth embodiment of the present invention for asolar battery module comprises a fluorocarbon resin sheet 1, a depositedinorganic oxide thin film 2 deposited on one of the surface of thefluorocarbon resin sheet 1, an ultraviolet absorbing layer 304 formed onthe other surface of the fluorocarbon resin sheet 1, and asoil-resistant layer 303 formed on the ultraviolet absorbing layer 304.The soil-resistant layer 303 forms the outermost surface of the frontsurface protective sheet A₁.

[0937] Referring to FIG. 26, a front surface protective sheet A₂ in athird example of the sixth embodiment of the present invention for asolar battery module comprises a fluorocarbon resin sheet 1, a depositedinorganic oxide thin film 2 formed on one of the surfaces of thefluorocarbon resin sheet 1, a soil-resistant layer 303 formed on thesurface of the fluorocarbon resin sheet 1, and an ultraviolet absorbinglayer 304 formed on the deposited inorganic oxide thin film 2. Thesoil-resistant layer 303 forms the outermost surface of the frontsurface protective sheet A₂.

[0938] In the front surface protective sheets shown in FIGS. 25 and 26,the surface of the fluorocarbon resin sheet 1 may be processed to form asurface-treated layer 3 therein.

[0939] Referring to FIG. 27, a front surface protective sheet A₃ in afourth example of the sixth embodiment of the present invention for asolar battery module comprises a fluorocarbon resin sheet 1, amultilayer film 4 consisting of at least two deposited inorganic oxidethin films 2 and formed on one of the surfaces of the fluorocarbon resinsheet 1, and a soil-resistant layer 303 and/or an ultraviolet asorbinglayer 304 formed on one of or both the surfaces of the fluorocarbonresin sheet 1 provided with the multilayer film 4.

[0940] Referring to FIG. 28, a front surface protective sheet A₄ in afifth example of the sixth embodiment of the present invention for asolar battery module comprises a fluorocarbon resin sheet 1, amultilayer film 5 consisting of at lest a deposited inorganic oxide thinfilm 2 a formed by a chemical vapor deposition process and a depositedinorganic oxide film 2 b formed on the deposited inorganic oxide thinfilm 2 a by a physical vapor deposition process, and formed on one ofthe surfaces of the fluorocarbon resin film 1, a soil-resistant layer303 and/or an ultraviolet absorber layer 304 formed on one of or boththe surfaces of the fluorocarbon resin sheet 1.

[0941] Referring to FIG. 29, a solar battery module T employs theprotective sheet A shown in FIG. 24 as its front surface protectivesheet. The solar battery module T is fabricated by superposing the frontsurface protective sheet A, a filler layer 12, a photovoltaic layer 13of solar cells, a filler layer 14 and a back surface protective sheet 15in that order in a superposed structure with the deposited inorganicoxide thin film 2 of the front surface protective sheet A facing inside,and subjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing.

[0942] The foregoing protective sheets in accordance with the presentinvention and the foregoing solar battery module employing thoseprotective sheets are examples intended to illustrate the invention andnot to be construed to limit the scope of the invention.

[0943] For example, the foregoing solar battery modules may compriseadditional layers for sunlight absorption, reinforcement or the like.

[0944] The soil-resistant layer 303 included in the front surfaceprotective sheet in accordance with the present invention and the solarbattery module is a coating film of a composite material containingphotocatalytic powder containing titanium oxide as a principal componentor a sol containing fine particles.

[0945] A solvent, aqueous or emulsion composite material containinga-photocatalytic powder for forming the coating film is prepared bypreparing a mixture of one or some kinds of photocatalytic powder, oneor some kinds of bonding agents as a vehicle, when necessary, additivesfor the improvement or modification of the workability, heat resistance,light resistance, water resistance, weather resistance, mechanical orchemical properties, dimensional stability, oxidation resistance,slipperiness, releasability, flame retardancy, antifungal property,electric properties and the like, such as a lubricant, a crosslinkingagent, an oxidation inhibitor, an ultraviolet absorber, a lightstabilizer, a filler, a reinforcing material, a stiffener, an antistaticagent, a flame retarder, a flame-resistant agent, a foaming agent, anantifungus agent, a pigment and the like, a solvent, and a diluent, andkneading the mixture. The concentration of each of the ingredients isdetermined so that the ingredients may not affect sunlighttransmittance. The coating film is formed by spreading the compositematerial by, for example, any one of coating processes including afloating-knife coating process, a knife-over-roll coating process, aninverted knife coating process, a squeeze roll coating process, areverse roll coating process, a roll coating process, a gravure rollcoating process, a kiss-roll coating process, an air blade coatingprocess, an extrusion coating process, a curtain-flow coating processand the like, or any one of printing processes including a gravureprinting process, an offset printing process, a silk-screen printingprocess, a transfer printing process and the like.

[0946] The desirable thickness of the coating film as dried is in therange of 0.1 to 10 g/m², more preferably, in the range of 0.5 to 1 g/m².

[0947] The photocatalytic powder may be a chemical substance havingfunctions to promote the degradation, destruction, decomposition orreduction in molecular weight of a resin due to oxidation or the likecaused by the operation of light, such as sun light, and to facilitatekeeping the surface of the soil-resistant layer clean by destroying theadhesion of dust to the surface of the soil-resistant layer and enablingwind and rain to remove dust from the surface of the soil-resistantlayer.

[0948] The photocatalytic powder may be powder of any one of, forexample, TiO₂. ZnO, SrTio₃, CdS, CaP, InP, GaAs, BaTiO₂, K₂TiO₃, K₂NbO₃,Fe₂)₃, Ta₂O₃, WO₃, SnO₂, Bi₂O₅, NiO, Cu₂O, SiC, SiO₂, MoS₂, InPb, RuO₂,CeO₂ and the like, any one of metals including Pt, Rh, RuO₂, Nb, Cu, Sn,Ni and Fe, or any one of composite material prepared by mixing one orsome of those metals and/or one or some of those metal oxides.

[0949] The photocatalytic powder content of the composite material isdependent on the shape and density of particles and a preferablephotocatalytic powder content is in the range of about 0.1 to about 30%by weight.

[0950] A bonding agent capable of forming a film, excellent in lightresistance, heat resistance, water resistance and the like, capable ofincreasing the hardness of the coatign film, excellent in scratchresistance and abrasion resistance and immune to the effect of thephotoactivity of the photocatalytic powder may e used as the vehicle.Possible materials for use as the bonding agent are, for example,polyethylene resins, polypropylene resins, ethylene-vinyl acetatecopolymers, ionomers, ethylene-ethyl acrylate copolymers,ethylene-acrylate or methacrylate copolymers, methyl pentene polymers,polybutene resins, polyvinyl chloride resins, polyvinyl acetate resins,vinyl chloride-vinylidene chloride copolymers, poly(meta)acrylic resins,polyacrylonitrile resins, polystyrene resins, acrylonitrile-styrenecopolymers (AS resins), Acrylonitrile-butadiene-styrene copolymers (ABSresins), polyester resins, polyamide resins, polycarbonate resins,polyvinyl alcohol resins, saponified ethylene_vinyl acetate copolymers,fluorocarbon resins, diene resins, polyacetal resins, polyurethaneresins, epoxy resins, phenolic resins, amino resins, silicone resins,nitrocellulose, inorganic polymers and the like, modified resins, and amixture of some of those resins.

[0951] It is particularly preferable to use one or some of low-meltingglass, alkali metal silicates, phosphates, colloidal silica andinorganic polymers among those bonding agents immune to the influence ofthe photocatalytic powder.

[0952] According to the present invention, an activity blocking layer303 a (FIG. 26) may be interposed between the soil-resistant layer 303and the ultraviolet absorbing layer or the fluorocarbon resin sheetunderlying the soil-resistant sheet 303 to prevent the degradation,decomposition or destruction of the ultraviolet absorbing layer or thefluorocarbon resin sheet due to the influence of the photoactivity ofthe photocatalytic powder contained in the soil-resistant layer 303.Generally, the activity blocking layer 303 a is formed under thesoil-resistant layer.

[0953] A transparent, deposited inorganic oxide thin film, such as adeposited silicon oxide thin film or a deposited aluminum oxide thinfilm, may be used as the activity blocking layer 303 a.

[0954] The deposited inorganic oxide thin film that serves as theactivity blocking layer can be formed by the foregoing film formingprocess. the thickness of the deposited inorganic oxide thin film is inthe range of about 100 to about 3000 Å, preferably, in the range of 100to 1500 Å.

[0955] When necessary, a bodning primer layer or the like may be usedfor forming the coating film of a composite material containingphotocatalytic powder and serving as the soil-resistant layer 303 toenhance the adhesion of the soil-resistant layer 303 to the underlyinglayer.

[0956] The bonding primer layer may be formed of, for example, amaterial capable of forming an inorganic primer layer that will not bedecomposed by the photoactivity of the photocatalytic powder containedin the soil-resistant layer. Representative materials suitable forforming the primer layer are alkyl titanates including tetraisopropyltitanate, tetrabutyl titanate and tetrastearyl titanate, a productobtained through the hydrolysis of titanium chelate, and inorganicpolysilazane (perhydropolysilazane).

[0957] In the present invention, tetraisopropyl titanate tetrabutyltitanate are particularly preferable because they are hydrolyzed veryquickly and can be decomposed after forming a coating.

[0958] Description will be given of the ultraviolet absorbing layer 304of the front surface protective sheet in accordance with the presentinvention for a solar battery module, and the solar battery module. Asolvent, aqueous or emulsion composite material for forming theultraviolet absorbing layer 304 is prepared by preparing a mixture ofone or some kinds of ultraviolet absorbers, one or some kinds of bondingagents as a vehicle photocatalytic powder, one or some kinds of bondingagents as a vehicle and, when necessary, additives for the improvementor modification of the workability, heat resistance, light resistance,water resistance, weather resistance, mechanical or chemical properties,dimensional stability, oxidation resistance, slipperiness,releasability, flame retardancy, antifungal property, electricproperties and the like, such as one or some of a lubricant, acrosslinking agent, an oxidation inhibitor, a stabilizer, a filler, areinforcing material, a stiffener, an antistatic agent, a flameretarder, a flame-resistant agent, a foaming agent, an antifungus agent,a pigment and the like, a solvent, and a diluent, and kneading themixture. The concentration of each of the ingredients is determined sothat the ingredients may not affect sunlight transmittance. The coatingfilm is formed by spreading the composite material by, for example, anyone of coating processes including a floating-knife coating process, aknife-over-roll coating process, an inverted knife coating process, asqueeze roll coating process, a reverse roll coating process, a rollcoating process, a gravure roll coating process, a kiss-roll coatingprocess, an air blade coating process, an extrusion coating process, acurtain-flow coating process and the like, or any one of printingprocesses including a gravure printing process, an offset printingprocess, a silk-screen printing process, a transfer printing process andthe like.

[0959] The desirable thickness of the coating film as dried is in therange of 0.1 to 10 g/m², more preferably, in the range of 0.5 to 1 g/m².

[0960] The ultraviolet absorber absorbs detrimental ultraviolet rayscontained in sunlight, converts the energy of ultraviolet rays intoharmless thermal energy in its molecules to prevent active species thatstarts the photodeterioration of polymers from being excited. One orsome of ultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

[0961] The ultraviolet absorber content of the composite material isdependent on the shape and density of the particles and a preferableultraviolet absorber content is in the range of about 0.1 to about 20%by weight.

[0962] The bonding agent used for preparing the composite material forforming the coating film serving as the dust-resistant layer andcontaining the photocatalytic powder may be used as the bonding agentserving as a vehicle.

EXAMPLES

[0963] Examples of the sixth embodiment will be described hereinafter.

Example 1

[0964] (1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet),i.e., base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polyvinyl fluoride sheet was unwound and woundaround a coating drum and a 300 Å thick deposited aluminum oxide thinfilm was deposited on a treated surface of the polyvinyl fluoride sheettreated for adhesion improvement by a reactive vacuum evaporationprocess of an electron beam (EB) heating system to form a coatedpolyvinyl fluoride sheet. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

[0965] Deposition conditions:

[0966] Evaporation source: Aluminum

[0967] Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

[0968] Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

[0969] EB power: 40 kW

[0970] Sheet moving speed: 600 m/min

[0971] (2) The 300 Å thick deposited aluminum oxide thin film of thecoated polyvinyl fluoride sheet was subjected to a glow-discharge plasmaprocess to form a plasma-processed surface. The glow-discharge plasmaprocess was carried out by a glow-discharge plasma producing apparatusof 1500 W in plasma output immediately after the deposition of the 300 Åthick deposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

[0972] An ultraviolet absorbing layer was formed in the plasma-processedsurface of the deposited aluminum oxide thin film to complete a frontsurface protective sheet in accordance with the present invention. Theultraviolet absorbing layer was formed by coating the plasma-processedsurface of the deposited aluminum oxide thin film with an ultravioletabsorber composite material containing 5 parts by weight of ultrafinetitanium oxide powder of 0.03 μm in particle size and 95 parts by weightof an ethylene-vinyl alcohol copolymer solution (30% solid content)in acoating rate of 0.5 g/m² (dry state) by a gravure coating process.

[0973] (3) A solar battery module in accordance with the presentinvention was fabricated by using the front surface protective sheetthus fabricated. The front surface protective sheet and a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells were superposed with theplasma-processed deposited aluminum oxide thin film facing inside andwith the surface of the 38 μm thick biaxially oriented polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet. Those component layerswere laminated by using an adhesive layer of an acrylic resin tocomplete a solar battery module.

[0974] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 2

[0975] (1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film),i.e., base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 300 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polyvinyl fluoride film treatedfor adhesion improvement under the following conditions to form a coatedpolyvinyl fluoride sheet.

[0976] Deposition conditions:

[0977] Reaction gas mixing ratio:Hexamethyldisilox-ane/oxygen/helium=1/10/10 (Unit: slm)

[0978] Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

[0979] Vacuum in deposition chamber: 6.0×10⁻⁶ mbar

[0980] Power supplied to cooling electrode drum: 20 kW

[0981] Film moving speed: 80 m/min

[0982] Surface for vapor deposition: Corona-processed surface

[0983] (2) The 300 Å thick deposited silicon oxide thin film of thecoated polyvinyl fluoride film was subjected to a corona dischargeprocess to form a corona-processed surface and to increase the surfacetension of the deposited silicon oxide thin film from 35 dyne to 60dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

[0984] An ultraviolet absorbing layer was formed on the corona-processedsurface of the deposited silicon oxide thin film to complete a frontsurface protective sheet in accordance with the present invention. Theultraviolet absorbing layer was formed by coating the corona-processedsurface of the deposited silicon oxide thin film with an ultravioletabsorber composite material containing 1 part by weight of abenzophenone ultraviolet absorber and 99 parts by weight of athermosetting acrylic resin solution (30% solid content) in a coatingrate of 2 g/m² (dry state) by a gravure coating process.

[0985] (3) A solar battery module was fabricated by using the frontsurface protective sheet thus fabricated. The front surface protectivesheet and a 38 μm thick biaxially oriented polyethylene terephthalatefilm provided with an array of amorphous silicon solar cells weresuperposed with the corona-processed deposited silicon oxide thin filmfacing inside and with the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

[0986] (4) Another protective sheet in accordance with the presentinvention and another solar battery module of the same components werefabricated by the same processes, except that a 50 μm thick fluorocarbonresin sheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 3

[0987] (1) A front surface protecting sheet in accordance with thepresent invention was fabricated by the same processes as those in (2)of Example 1, except that, after forming the ultraviolet absorber layeron the plasma-processed surface of the deposited aluminum oxide thinfilm in (2) of Example 1, a soil-resistant layer of 1 g/m² (dry state)in coating rate was formed on the outer surface of the 50 μm thickpolyvinyl fluoride film as a base sheet by spreading a photocatalyticcomposite material containing 10 parts by weight of ultrafine titaniumoxide powder of 0.03 μm in particle size and 90 parts by weight of atetraethoxysilane solution (20% solid content) by a gravure roll coatingprocess.

[0988] A solar battery module provided with the front surface protectivesheet thus fabricated was fabricated by the same process as that inExample 1.

Example 4

[0989] (1) A front surface protecting sheet in accordance with thepresent invention was fabricated by the same processes as those in (2)of Example 2, except that, after forming the ultraviolet absorber layeron the corona-processed surface of the deposited silicon oxide thin filmin (2) of Example 2, a soil-resistant layer of 1 g/m² (dry state) incoating rate was formed on the outer surface of the 50 μm thickpolyvinyl fluoride film as a base sheet by spreading a photocatalyticcomposite material containing 10 parts by weight of ultrafine titaniumoxide powder of 0.03 μm in particle size and 90 parts by weight of atetraethoxysilane solution (20% solid content) by a gravure roll coatingprocess.

[0990] A solar battery module provided with the front surface protectivesheet thus fabricated was fabricated by the same process as that inExample 1.

Example 5

[0991] A front surface protecting sheet in accordance with the presentinvention was fabricated by the same processes as those in (2) ofExample 1, except that, an ultraviolet absorber layer was formed on asurface of the 50 μm thick polyvinyl fluoride film as a base sheetopposite the surface of the same on which the deposited aluminum oxidethin film was formed by the same process as that in Example 1 in (2) ofExample 1 instead of forming the same on the plasma-processed surface ofthe deposited aluminum oxide thin film, and a soil-resistant layer of 1g/m² (dry state) in coating rate was formed on the outer surface of the50 μm thick polyvinyl fluoride film by spreading a photocatalyticcomposite material containing 10 parts by weight of ultrafine titaniumoxide powder of 0.03 μm in particle size and 90 parts by weight of atetraethoxysilane solution (20% solid content) by a gravure roll coatingprocess.

[0992] A solar battery module provided with the front surface protectivesheet thus fabricated was fabricated by the same process as that inExample 1.

Comparative Example 1

[0993] (1) A solar battery module was fabricated by superposing a 50 μmthick polyvinyl fluoride film (PVF film) as a base sheet and a 38 μmthick biaxially oriented polyethylene terephthalate film provided withan array of amorphous silicon solar cells with the surface of the 38 μmthick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

Comparative Example 2

[0994] A solar battery module was fabricated by superposing a 50 μmthick fluorocarbon resin sheet of anethylene-polytetrafluoroethylenecopolymer film (ETFE film) as a base sheet, as a front surfaceprotective sheet and a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

[0995] Experiments

[0996] The protective sheets in Examples 1 to 5 of the present inventionand those in Comparative examples 1 and 2 were subjected to totaltransmittance measurement. The solar battery modules in Examples 1 to 5and Comparative examples 1 and 2 were subjected to solar battery moduleevaluation tests.

[0997] (1) Total Transmittance Measurement

[0998] Total transmittance (%) of each of the protective sheets inExamples 1 to 5 and Comparative examples 1 and 2 against the totaltransmittance of the base sheet as a reference total transmittance wasmeasured by a color computer.

[0999] (2) Solar Battery Module Evaluation Tests

[1000] The solar battery modules were subjected to environmental testsin conformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

[1001] (3) Moisture Permeability and Oxygen Permeability The moisturepermeabilities of the protective sheets in Examples 1 to 5 andComparative examples 1 and 2 were measured in an atmosphere of 40° C.and 90% RH by a moisture permeability measuring apparatus (PERMATRAN,MOCON, USA). The oxygen permeabilities of the protective sheets inExamples 1 to 5 and Comparative examples 1 and 2 were measured in anatmosphere of 23° C. and 90% RH by an oxygen permeability measuringapparatus (OXTRAN, MOCON, USA).

[1002] Measured data is tabulated in Table 6-1. TABLE 6-1 Total MoistureOxygen Output trans- permea- permea- reduction mittance bility bilityRatio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%) Example 1 92 0.8 1.4 4Example 2 93 0.5 1.0 2 Example 3 90 0.8 1.4 3 Example 4 91 0.5 1.0 2Example 5 92 0.8 1.4 4 Comparative 93 26.3  27.7 15  Example 1Comparative 95 11.2  ≧500 14  Example 2

[1003] In table 6-1, moisture permeability is expressed in a unit ofg/m²/day•40° C.•100% RH, and oxygen permeability is expressed in a unitof cc/m²/day•23° C.•90% RH.

[1004] As obvious from Table 6-1, the protective sheets in Examples 1 to5 have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

[1005] The output reduction ratios of the solar battery modulesemploying the protective sheets in Examples 1 to 55 were low.

[1006] The protective sheets in Comparative examples 1 and 2 had hightotal transmittances, respectively. However, the moistureimpermeabilities and the oxygen impermeabilities of the protectivesheets in Comparative examples 1 and 2 were low. Consequently, theoutput reduction ratios of the solar battery modules employing theprotective sheets in Comparative examples 1 and 2 were high.

[1007] As apparent from the foregoing description, the present inventiontakes into consideraion the characteristics of a glass sheet thatis-used as the front surface protective sheet of a solar battery module,photocatalytic powder and an ultraviolet absorber, uses a fluorocarbonresin sheet as a base sheet, fabricates a coated fluorocarbon resinsheet by forming a transparent, vitreous deposited inorganic oxide thinfilm, such as a silicon oxide thin film or an aluminum oxide thin film,on one of the surfaces of the fluorocarbon resin sheet, and fabricates aprotective sheet for a solar battery module by forming a soil-resistantlayer of a composite material containing a photocatalytic powder and/oran ultraviolet absorbing layer of a composite material containing anultraviolet absorber on one of or both the surfaces of the fluorocarbonresin sheet, and forms a solar battery module by using the protectivesheet as a front surface protective sheet by superposing the protectivesheet as a front surface protective sheet, a filler layer, a filmprovided with solar cells, i.e., photovoltaic cells, a filler layer anda back surface protective sheet in that order in a superposed structurewith the deposited inorganic oxide thin film facing inside, bringing thecomponent layers of the superposed structure into close contact byvacuum and bonding together those component layers by a laminationprocess using hot pressing. The protective sheet has greatly improvedmoisture resistance to prevent the permeation of moisture and oxygenthrough the protective sheet, is excellent in light resistance, heatresistance and water resistance, limits performance degradation due toaging to the least extent, is excellent in protective ability, preventssoiling of its surface by accumulated dust, can be fabricated at a lowcost and can be used for the fabrication of a low-cost, safe solarbattery module.

[1008] The materials mentioned in the description of the first, thesecond, the third, the fourth and the fifth embodiment are applicable tothe sixth embodiment.

[1009] Seventh Embodiment

[1010] A protective sheet (cover film) in a seventh embodiment accordingto the present invention is used as the front or the back surfaceprotective sheet of a solar battery module and comprises at least a basefilm (weather-resistant sheet), an ultraviolet intercepting layer, aninfrared intercepting layer or a highly reflective layer formed on thebase film.

[1011] The protective sheet in the seventh embodiment of the foregoingconstruction has the following effects.

[1012] (1) The protective sheet is a laminated film comprising at leasta base film and one or some of an ultraviolet intercepting layer, aninfrared intercepting layer and a highly reflective layer. Theprotective sheet is capable of intercepting some types of lightradiation with wavelengths that do not contribute to power generation,such as ultraviolet radiation and infrared radiation to prevent thedegradation of solar cells attributable to the effect of those types oflight radiation. The use of a laminated film formed by laminating a basefilm and a highly reflective layer as a back surface protective sheetdisposed on the back side of solar cells improves power generatingefficiency.

[1013] (2) The protective sheet (cover film) for a solar battery modulecan be produced at a high productivity by forming an ultravioletintercepting layer, an infrared intercepting layer and a highlyreflective layer on a long, wide base film by a continuous coating meansor evaporation means.

[1014] (3) A glass sheet serving as the front surface protective sheetof a solar battery module can be replaced with the protective sheet(cover film) of the present invention. The protective sheet of thepresent invention is easy to handle, improves the productivity of aproduction line for producing solar battery modules, enables theformation of a solar battery module in lightweight construction at areduced cost.

[1015] The ultraviolet intercepting layer is a coating resin filmcontaining dispersed metal oxide particles of a mean particle size inthe range of 1 to 1000 nm.

[1016] Since the coating resin film containing disperse metal oxideparticles is capable of satisfactorily intercepting ultravioletradiation, the protective sheet (cover film) has a satisfactoryultraviolet intercepting ability.

[1017] Accordingly, the ultraviolet degradation of the solar battery canbe prevented by covering the solar cells with the protective sheet.

[1018] The metal oxide particles are those of TiO₂, ZnO, α-Fe₂O₃ orCeO₂.

[1019] Since the coating resin film containing the dispersed metal oxideparticles is excellent in ultraviolet intercepting ability andstability, the protective sheet has an excellent ultravioletintercepting ability.

[1020] The ultraviolet degradation of a solar battery can be suppressedfor a long period of use by covering the solar cells of the solarbattery with the protective sheet.

[1021] The infrared intercepting layer is a deposited metal film or acoating resin film containing dispersed metal oxide particles.

[1022] Since the deposited metal film or the coating resin filmcontaining the disperse metal oxide particles has a satisfactoryinfrared intercepting ability, the protective sheet for a solar batterymodule has a satisfactory infrared intercepting ability.

[1023] Accordingly, the infrared degradation (heat degradation) of asolar battery can be prevented by covering the solar cells of the solarbattery with the protective sheet (cover film).

[1024] The deposited metal film is a deposited film of Al or Ag.

[1025] Since the deposited film of Al or Ag is excellent in infraredintercepting ability and long-term stability, the protective sheet hasan excellent infrared intercepting ability.

[1026] Accordingly, the infrared degradation of a solar battery can beprevented for a long period of use by covering the solar cells of thesolar battery with the protective sheet (cover film).

[1027] The deposited metal film intercepts visible radiation if the sameis excessively thick. Therefore, it is preferable to incorporate thedeposited metal film into a protective sheet for use as a back surfaceprotective sheet.

[1028] The metal oxide particles are those of SnO₂ capable ofefficiently absorbing infrared radiation.

[1029] Since the coating resin film containing dispersed SnO₂ particlesis capable of efficiently intercepting infrared radiation and excellentin long-term stability, the protective sheet including the coating resinfilm containing dispersed SnO₂ particles has an excellent infraredintercepting ability.

[1030] Accordingly, the infrared degradation of a solar battery can beprevented for a long period of use by covering the solar cells of thesolar battery with the protective sheet (cover film).

[1031] The highly reflective layer is a deposited Ag or Al film or aresin film containing a dispersed white pigment.

[1032] The resin film containing the dispersed white pigment may be awhite film formed by spreading a mixture of a weather-resistant resin,such as a fluorocarbon resin or a highly weather-resistant polyethyleneterephthalate resin, and a white pigment or a weather-resistant filmformed by coating a weather-resistant film, such as a fluorocarbon resinfilm or a highly weather-resistant biaxially oriented polyethyleneterephthalate film (hereinafter referred to as “PET film”), with a whiteresin film formed by applying a liquid resin containing a dispersedwhite pigment in a film to the weather-resistant film and drying thefilm.

[1033] Since the deposited Ag or Al film or the resin film containingthe dispersed white pigment is highly reflective, the protective sheethas a high light reflecting ability.

[1034] Accordingly, a solar battery module provided with the protectivesheet bonded to the back surface of a photovoltaic layer provided withsolar cells reflects part of incident light fallen on the front surfaceof the solar battery module and penetrated the solar cells toward thesolar cells, which improves the power generating efficiency of the solarbattery module.

[1035] A protective sheet fabricating method in accordance with thepresent invention fabricates a protective sheet for a solar batterymodule. The protective sheet comprises a laminated film at leastcomprising a weather-resistant sheet (base film) and an ultravioletintercepting layer formed on the base film. The ultraviolet interceptinglayer is formed by applying a liquid resin containing dispersed TiO₂ orCeO₂ particles having a mean particle size in the range of 1 to 1000 nmin a film to the base film and drying the film.

[1036] The protective sheet (cover film) for a solar battery moduleprovided with an ultraviolet intercepting layer can be produced at ahigh productivity and low cost by forming an ultraviolet interceptinglayer on a long, wide base film moving at a high moving speed on acontinuous coating means.

[1037] A protective sheet fabricating method in accordance with thepresent invention may form a coating primer layer on a surface of thebase film on which the liquid resin containing dispersed TiO₂ or CeO₂particles is to be applied.

[1038] Thus, the base film of the protective sheet and the coating resinfilm containing dispersed TiO₂ or Ceo₂ particles can firmly bondedtogether.

[1039] Even if a solar battery module provided with the protective sheetin accordance with the present invention is used under severe outdoorconditions, the ultraviolet intercepting layer will not come off thebase film and solar battery module has improved stability.

[1040] A protective sheet fabricating method in accordance with thepresent invention fabricates a protective sheet for a solar batterymodule. The protective sheet comprises a laminated film at leastcomprising a weather-resistant sheet (base film) and an infraredintercepting layer formed on the base film. The infrared interceptinglayer is a deposited metal film deposited on the base film or a coatingresin film formed by applying a liquid resin containing dispersed metaloxide particles in a film to the base film and drying the film.

[1041] The protective sheet (cover film) for a solar battery moduleprovided with an infrared intercepting layer can be produced at a highproductivity and low cost by forming an infrared intercepting layer on along, wide base film moving at a high moving speed on a continuousdeposition or coating means.

[1042] A solar battery module in accordance with the present inventionis provided with the protective sheet bonded to the front surface of alayer provided with solar cells by a heat-adhesive filler layer.

[1043] The heat-adhesive filer layer may be formed of a heat-adhesiveresin containing as a principal component, for example, anethylene-vinyl acetate copolymer, a polyolefin resin, a polyvinylbutyral resin or a silicone resin.

[1044] The solar cells can be embedded in the heat-adhesive filler layerin a stable state, and can be sandwiched between the protective sheetexcellent in ultraviolet intercepting ability, infrared interceptingability and light reflecting ability. Consequently, ultraviolet andinfrared radiation which does not contribute to power generation can beintercepted, the highly reflective layer disposed behind the solar cellsimproves power generating efficiency, and the solar battery module isexcellent in durability and generates power at a high power generatingefficiency.

[1045] Protective sheets (cover films) in the seventh embodiment for asolar battery module and solar battery modules employing the protectivesheets will be described with reference to the accompanying drawings.

[1046] The present invention is not limited in its practical applicationto those shown in the drawings.

[1047] FIGS. 30 to 33 are typical sectional views of examples ofprotective sheets in the seventh embodiment for solar battery modules.

[1048] Referring to FIG. 30, a protective sheet 410 in a first exampleof the seventh embodiment of the present invention for a solar batterymodule comprises at least a base film 401 (weather-resistant sheet) 401and an ultraviolet intercepting layer 402 formed on one of the surfacesof the base film 401.

[1049] Preferably, the base film 401 is a durable film excellent inweather resistance, strength and ressitances to detrimental effects,such as a polyvinyl fluoride film (hereinafter referred to as “PVFfilm”), a fluorocarbon resin film, succh as anethylene-tetrafluoroethylene copolymer film (hereinafter referred to as“ETFE film”), a highly weather-resistant biaxially oriented polyethyleneterephthalate film (hereinafter referred to as “weather-resistant PETfilm”), a polycarbonate film or a polyacrylate film.

[1050] The ultraviolet intercepting layer 402 may be a coating resinfilm containing dispersed metal oxide particles having a mean particlesize in the range of 1 to 1000 nm. Preferable metal oxide particles areparticles of TiO₂, ZnO, α-Fe₂O₃ or Ceo₂. TiO₂ or CeO₂ particles areparticularly preferable.

[1051] Particles of one of those metal oxides or a mixture of some ofthose metal oxides may be used.

[1052] An acrylic resin or a silicone resin may be used as a binder forholding the particles together. An additive, such as a crosslinkingagent or a silane coupling agent may be added to the resin to enhancethe weather resistance of the resin.

[1053] A primer layer 402 a of a polyisocyanate primer or apolyacryamine primer may be formed on a surface of the base film 401 onwhich the ultraviolet intercepting layer 402 is to be formed to enhanceadhesion between the base film 401 and the ultraviolet interceptinglayer 402 before forming the ultraviolet intercepting layer 402 on thebase film by a coating process.

[1054] The protective film 401 intercepts ultraviolet radiation andtransmits visible radiation. In most cases, the protective sheet is usedas a front surface protective sheet to be disposed on the lightreceiving side of a solar battery module.

[1055] Referring to FIG. 31, a protective sheet 420 in a second exampleof the seventh embodiment of the present invention for a solar batterymodule comprises at least a base film 401 and an infrared interceptinglayer 403 formed on a surface of the base film 401.

[1056] When necessary, a primer layer 403 a may be sandwiched betweenthe base film 401 and the infrared intercepting layer 403 to enhanceadhesion between the base film 401 and the infrared intercepting layer403.

[1057] The base film 401 may be formed of the same material as the basefilm 401 of the example shown in FIG. 30. The infrared interceptinglayer 403 may be a coating resin layer containing dispsersed metal oxideparticles, such as SnO₂ particles.

[1058] The same resin as that used for forming the ultravioletintercepting layer may be used as a binder for holding the metal oxideparticles.

[1059] It is preferable that the infrared intercepting layer 403contains metal oxide particles, such as SnO₂ particles when theprotective sheet 420 is used as the front surface protective sheet of asolar battery module. It is preferable that the infrared interceptinglayer 403 is a deposited Al or Ag film when the protective sheet 420 isused as the back surface protective sheet of a solar battery module.

[1060] Referring to FIG. 32, a protective sheet 430 in a third exampleof the seventh embodiment of the present invention for a solar batterymodule comprises at least a base film 401, an ultraviolet interceptinglayer 402 formed on the base film 401, and an infrared interceptinglayer 403 formed on the ultraviolet intercepting layer 402.

[1061] When necessary, a primer layer 402 a may be sandwiched betweenthe base film 401 and the ultraviolet intercepting layer 402, and aprimer layer 403 a may be sandwiched between the ultravioletintercepting layer 402 and the infrared intercepting layer 403 toenhance adhesion between the contiguous layers. When the infraredintercepting layer 403 is a deposited metal film, a primer for depositedmetal film may be used.

[1062] Materials forming the base film 401, the ultraviolet interceptinglayer 402 and the infrared intercepting layer 403 may be those of theexamples shown in FIGS. 30 and 31 and hence the further descriptionthereof will be omitted.

[1063] When the infrared intercepting layer 403 is a coating resin layercontaining dispersed metal oxide particles, such as SnO₂ particles, theprotective sheet 430 intercepts ultraviolet radiation and infraredradiation and transmits visible radiation. Therefore, the protectivesheet 430 is suitable for use as a front surface protective sheet. Theprotective sheet 430 intercepts visible radiation as well as ultravioletradiation and infrared radiation when the infrared intercepting layer403 is a deposited metal film. Therefore, the protective sheet issuitable for use as a back surface protective sheet.

[1064] Referring to FIG. 33, a protective sheet 440 in a fourth exampleof the seventh embodiment of the present invention for a solar batterymodule comprises at least a base film 401′ and a highly reflective layer404 formed on the base film 401′.

[1065] When necessary, a primer layer may be sandwiched between the basefilm 401′ and the highly reflective layer 404 to enhance adhesionbetween the base film 401′ and the highly reflective layer 404.

[1066] The base film 401′ may be the same as the base films 401 of theprotective sheet shown in FIGS. 30 to 32. A highly reflective depositedAg or Al film or a resin film containing dispersed white pigment isparticularly suitable for use as the highly reflective layer 404.

[1067] The protective sheet 440 thus constructed is used as the backsurface protective sheet of a solar battery module. Part of incidentlight fallen on the front surface of the solar battery module andpenetrated the solar cells is reflected toward the solar cells, whichimproves the power generating efficiency of the solar battery module.

[1068] When necessary, each of the protective sheets shown in FIGS. 30to 34 for solar battery modules may additionally be provided with, forexample, a deposited inorganic oxide film, such as an aluminum oxidefilm or a silicon oxide film (SiOx film), or each of the layers formedon the base films may be coated with a protective layer.

[1069] Generally, a filler layer is interposed between the front surfaceof a photovoltaic layer provided with solar cells and the protectivesheet when bonding the protective sheet to the photovoltaic layer. Ifadhesion between the protective sheet and the filler layer is not highenough, an adhesive layer may be formed on a surface of the protectivesheet to be bonded to the photovoltaic layer.

[1070] Referring to FIG. 34 showing a solar battery module in a typicalsectional view, protective sheets in accordance with the presentinvention are bonded to the front and the back surface of a photovoltaiclayer provided with solar cells.

[1071] A solar battery module 400 shown in FIG. 34 is formed bysuperposing, from the front side toward the back side, a base film 401,an ultraviolet intercepting layer 402, an infrared intercepting layer403, a filler layer 405, a photovoltaic layer 406 provided with solarcells, a filler layer 405′, a highly reflective layer 404 and a basefilm 401′, and laminating those component layers.

[1072] The photovoltaic layer 406 is sandwiched between the fillerlayers 405 and 405′, a protective sheet comprising the base film 401,the ultraviolet intercepting layer 402 and the infrared interceptinglayer 403 is bonded to the front surface of the photovoltaic layer 406,and a protective sheet comprising the base film 401′ and the highlyreflective sheet 404 is bonded to the back surface of the photovoltaiclayer 406.

[1073] Therefore, ultraviolet radiation and infrared radiation that donot contribute to power generation and promotess the degradation ofsolar cells are intercepted by the protective sheet and, consequently,the degradation of the solar cells is prevented and the durability ofthe solar battery module is improved.

[1074] Visible radiation that contributes to power generation travelsthrough the front protective sheet and falls on the solar cells to causethe solar cells to generate power. Part of visible radiation penetratedthe photovoltaic layer 406 is reflected by the highly relfective layer404 so as to fall again on the solar cells, so that visible radiation isused effectively for power generation and the efficiency ofphotoelectric conversion is improved.

EXAMPLES

[1075] Examples of the seventh embodiment will be described hereinafter.

Example 1

[1076] A front surface protective sheet for a solar battery modulecomprises a 70 μm thick highly weather-resistant PET film, and aninfrared intercepting layer of an acrylic resin containing dispersedSnO₂ particles formed on one surface of the PET film. A back surfaceprotective sheet is a laminated film formed by superposing a 38 μm thickPVF film, a 50 μm thick aluminum foil and a 38 μm thick PVF film in thatorder and laminating those component layers by a dry lamination process.A solar battery module in Example 1 was fabricated by bonding the frontsurface protective sheet and the back surface protective sheet to thefront and the back surface, respectively, of a photovoltaic layerprovided with an array of crystal silicon solar cells with 500 μm thickethylene-vinyl acetate copolymer films, i.e., heat-adhesive fillerlayers, by a vacuum lamination process.

Example 2

[1077] A solar battery module in Example 2 was fabricated by using thesame components as those of the solar battery module in Example 1 by thesame processes as in Example 1, except that a front surface protectivesheet comprising a 70 μm thick highly weather-resistant PET film, anultraviolet intercepting layer of an acrylic resin containing dispersedTiO₂ particles having a mean particle size of 10 nm formed on the PETfilm, and an infrared intercepting layer of an acrylic resin containingdispersed SnO₂ particles was used instead of the front surfaceprotective sheet of Example 1.

Example 3

[1078] A solar battery module in Example 3 was fabricated by using thesame components as those of the solar battery module in Example 1 by thesame processes as in Example 1, except that a front surface protectivesheet comprising a 70 μm thick highly weather-resistant PET film and anultraviolet intercepting layer of an acrylic resin containing dispersedTiO₂ particles having a mean particle size of 10 nm formed on the PETfilm was used instead of the front surface protective sheet of Example1.

Example 4

[1079] A solar battery module in Example 4 was fabricated by using thesame components as those of the solar battery module in Example 1 by thesame processes as in Example 1, except that a front surface protectivesheet similar to that in Example 2 and comprising a 70 μm thick highlyweather-resistant PET film, an ultraviolet intercepting layer of anacrylic resin containing dispersed TiO₂ particles having a mean particlesize of 10 nm formed on the PET film, and an infrared intercepting layerof an acrylic resin containing dispersed SnO₂ particles formed on theultraviolet intercepting layer was used instead of the front surfaceprotective sheet of Example 1, and a back surface protective sheetcomprising a 70 μm thick highly weather-resistant PET film, and a backsurface protective sheet comprising a 70 μm thick highlyweather-resistant PET film and an 800 Å thick deposited Al film formedas a highly reflective layer on the PET film was used instead of theback surface protective sheet of Example 1.

Comparative Example 1

[1080] A solar battery module in Comparative example 1 was fabricated byusing the same components as those of the solar battery module inExample 1 by the same processes as in Example 1, except that a 70 μmthick highly weather-resistant PET film not provided with any infraredintercepting layer was used as a front surface protective sheet.

[1081] Evaluation of Solar Battery Modules in Examples 1 to 4 andComparative Example 1

[1082] The solar battery modules in Examples 1 to 4 and Comparativeexample 1 were subjected to tests to evaluate their performance andlong-term reliability, in which photoelectric conversion efficiency η(%) and fill factor (FF) were measured in an initial state and in astate after irradiation with 1 sun, for 2000 hr. Measured data istabulated in Table 7-1. TABLE 7-1 Characteristic of solar battery Stateafter exposure Initial state to 1 sun, 2000 hr Conversion Conversionefficiency efficiency η (%) FF η (%) FF Example 1 10.5 0.65 10.2 0.60Example 2 10.4 0.63 10.1 0.59 Example 3 10.5 0.66 10.3 0.60 Example 411.5 0.70 10.8 0.65 Comparative 10.4 0.62  9.5 0.58 Example 4

[1083] As obvious from the measured data shown in Tables 7-1, the solarbattery modules in Examples 1 to 4 have conversion efficiencies notsmaller than 10% in an initial state and in a state after exposure tosunlight for 2000 hr, and the initial conversion efficiencies of thesolar battery modules in Examples 1 to 4 were not reduced significantlyby sunlight irradiation. The conversion efficiency of the solar batterymodule in Comparative example 1 was reduced to 9.5% by sunlightirradiation, and the conversion efficiency reduction ratio was large.

[1084] As is apparent from the foregoing description, the solar batterymodules of the present invention are excellent in performance andlong-term reliability. The protective sheet of the present invention andthe solar battery module provided with the same protective sheet can befabricated easily at a high productivity and are economicallyadvantageous.

[1085] The materials mentioned in the description of the first to thesixth embodiment are applicable to the seventh embodiment.

[1086] Eighth Embodiment

[1087] Basic Construction

[1088] A protective sheet (film) in an eighth embodiment according tothe present invention is intended for use as a front surface protectivesheet of a solar battery module for covering the front surface of aphotovoltaic layer provided with solar cells. The protective sheet is asingle weather-resistant sheet (base film) or is a laminated sheetcomprising a plurality of layers including a base film and at least onelight confining layer.

[1089] The protective sheet (protective film) for a solar battery modulecan effectively be used as a substrate for the photovoltaic layer. Thematerial and thickness of the base film are determined properlyaccording to the use of the protective sheet. A film meetingrequirements for strength, heat resistance, weather resistance,transparency and the like is used as the base film.

[1090] The protective sheet in accordance with the present invention fora solar battery module has a function to confine light and hence lightfallen on the solar cells can repeatedly be used, which enhances powergenerating efficiency.

[1091] A protective sheet (film) in accordance with the presentinvention is intended for use as a front surface protective sheet of asolar battery module for covering the front surface of a photovoltaiclayer provided with solar cells. The protective sheet is a singleweather-resistant sheet (base film) or is a laminated sheet comprising aplurality of layers including a base film, at least one light confininglayer, and an adhesive layer for bonding the protective sheet to aphotovoltaic layer provided with solar cells.

[1092] A protective sheet of such laminated construction having a basefilm, a light confining layer and the adhesive layer for bonding theprotective sheet to a surface of a photovoltaic layer is suitableparticularly for use as a protective sheet for a solar battery module.

[1093] When the protective sheet for a solar battery module is thusconstructed, it is not necessary to sandwich an adhesive film providedwith a soft, sticky adhesive layer and difficult to handle between theprotective sheet and the photovoltaic layer provided with solar cells.The adhesive layer need not be formed in a great thickness to facilitatehandling the protective sheet and may be formed in the least necessarythickness. The protective sheet simplifies laminating process andimproves productivity.

[1094] When the light confining layer is formed on the adhesive layer,i.e., when the light confining layer is the innermost layer of theprotective sheet to be brought into contact with the photovoltaic layer,a peripheral portion of the light confining layer is removed so that aperipheral portion of the adhesive layer is exposed, and the protectivesheet can be bonded to the photovoltaic layer with the exposedperipheral portion of the adhesive layer.

[1095] According to the present invention, the light confining layer hasan irregular surface comprising regularly arranged projections. Theheight of the projections or depth of recesses between the projectionsis in the range of 0.1 nm to 500 μm.

[1096] Preferably, the irregular surface of the light confining layer isformed by arranging ridges or furrows of a triangular, trapezoidal orsemicircular cross section having inclined surfaces, projections orrecesses having the shape of a pyramid, a frustum, a hemisphere, a roundprojection or the like. An irregular surface formed by arrangingpyramidal projections or recesses having intersecting surfaces formingan angle (apex angle) of 90° is particularly preferable.

[1097] Preferably, the height or depth of the irregularities is in therange of 0.1 nm to 500 μm. When the height or depth of theirregularities is less than 0.1 nm or greater than 500 μm, the effect ofthe light confining layer to confine light thereto by refracting andreflecting light is not high enough.

[1098] The appropriate range of the height or depth of theirregularities is dependent on the type of the solar battery module. Forexample, a suitable range of the height or depth of the irregularitiesis 0.1 nm to 500 nm when thin-film solar cells, such as amorphoussilicon solar cells, are employed, and is 1 to 500 μm when thick solarcells, such as single-crystal silicon solar cells, are employed.

[1099] A light confining layer meeting such conditions has a furthereffective light confining function.

[1100] According to the present invention, a light confining layer mayhave an irregular surface having large irregularities of a height ordepth in the range of 1 to 500 μm, and small irregularities of a heightor depth in the range of 0.1 to 500 nm formed on the largeirregularities.

[1101] This light confining layer is capable of further effectivelyconfining light fallen on the solar cells by effectively refracting andreflecting the incident light.

[1102] At least the base film of the protective sheet for a solarbattery module is a weather-resistant film.

[1103] Thus, the protective sheet has an improved weather resistance.When the protective sheet is bonded to the front surface of thephotovoltaic layer provided with the solar cells, the power generatingperformance of the solar cells is improved, the solar cells can safelybe protected for a long period of use, and the solar battery module hasexcellent long-term reliability.

[1104] The component layers of the protective sheet for a solar batterymodule may include a gas-barrier layer.

[1105] The protective sheet of the present invention is used, in mostcases, as a front surface protective sheet for covering the lightreceifing surface of a photovoltaic layer provided with solar cells.Therefore, it is preferable that the gas-barrier layer has a hightransmittance particularly to visible radiation. Preferable layers foruse as the gas-barrier layer are deposited layers of, for example,silicon oxide (Sio_(x)), silicon nitride (SiN_(x)), aluminum oxide(Al_(x)O_(y)) and the like, or inorganic-organic hybrid layers.

[1106] The gas-barrier layer improves the gas impermeability, i.e.,impermeability to moisture, oxygen and the like, of the protectivesheet.

[1107] Those gas-barrier layers may be used individually or incombination in a composite layer.

[1108] The gas-barrier layer improves the impermeability to moisture,oxygen and the like of the protective sheet, and the protective sheet issuitable for use in combination with polycrystalline or microcrystallinesilicon thin-film solar cells subject to degradation by moisture oroxygen or tandem solar cells comprising, in combination, polycrystallineor microcrystalline silicon thin-film solar cells, and amorphoussilicon, amorphous silicon-germanium or copper-selenium solar cells.

[1109] According to the present invention, the protective sheet for asolar battery module is placed on at least one of the surfaces of aphotovoltaic layer provided with solar cells.

[1110] Since the protective sheet in accordance with the presentinvention is excellent, as mentioned above, in strength, heatresistance, weather resistance, transparency and gas impermeability andhas a light confining function, the incident light can effectively usedfor power generation, and the solar battery module employing theprotective sheet of the present invention is excellent in long-termreliability and is capable of efficiently generating power.

[1111] The use of the protective sheet provided with the adhesive layersimplifies the solar battery module fabricating process, and enables thefabrication of a solar battery module excellent in long-termreliability, performance and productivity.

[1112] Materials for fabricating protective sheet (protective film) inaccordance with the present invention for solar battery modules andprotective sheet fabricating methods will be described hereinafter.

[1113] Preferably, a weather-resistant sheet (base film) for aprotective sheet in accordance with the present invention for a solarbattery module is excellent in strength, heat resistance andtransparency (transmittance to visible radiation) as well as in weatherresistance. Possible films as the base film are, for example,fluorocarbon resins films, such as polyvinyl fluoride films (PVF films)and ethylene-tetrafluoroethylene copolymer films (ETFE films),polycarbonate films, polyethersulfone films, polysulfone films,polyacrylonitrile films, acrylic resin films, cellulose acetate films,glass-fiber-reinforced polycarbonate films, weather-resistantpolyethylene terephthalate films and weather-resistant polypropylenefilms.

[1114] Those films may be used either individually or in combination incomposite films.

[1115] Preferably, the gas-barrier layer formed of a gas-barier materialis transparent, heat-resistant and weather-resistant as well asexcellent in impermeability. From this point of view, suitablegas-barrier layers are deposited films of one of silicon oxide(Sio_(x)), silicon nitride (SiN_(x)), tin oxide (SnO_(x)) and aluminumoxide (Al_(x)O_(y)), deposited films each of a mixture of some of thosemetal oxides, or composite films each of some of those metal oxides.

[1116] The deposited silicon oxide films(SiO_(x) films), silicon nitridefilms (SiN_(x) films), tin oxide films (SnO_(x) films and aluminum oxidefilms (Al_(x)O_(y) films can easily be formed by a CVD process, a PE-CVD(plasma-enhanced CVD) process, a PVD process and a sputtering process,respectively, on a base film. The PE-CVD process is particularlypreferable because the same is capable of depositing a dense,transparent deposoted film at a low temperature.

[1117] A suitable thickness of the deposited film is in the range of 50to 5000 Å, preferably, in the range of 300 to 1500 Å.

[1118] The inorgaic-organic hybrid coating layer may be formed of, forexample, tetraethoxysilane and an ethylene-vinyl alcohol copolymer.Coating liquids of those materials are prepared, and the coating liquidsare applied to the base film in films by a gravure roll coating processor the like and hot-drying the films.

[1119] Preferably, the inorgaic-orgaic hybrid coating layer is formed ina coating rate (dry state) in the range of 0.5 to 8 g/m², morepreferably, in the range of 1 to 5 g/m².

[1120] The inorganic-organic hybrid coating layer is excellent in gasimpermeability and may be used individually. The inorganic-organichybrid coating layer may be formed on a deposited inorganic oxide filmto enhance the gas impermeability of the deposited inorganic oxide film.

[1121] An adhesive layer to be formed beforehand on a protective sheetto bond the protective sheet to a photovoltaic layer provided with solarcells may be formed of any one of ethylene copolymers includingethylene-vinyl acetate copolymers, ethylene-acrylate copolymers andethylene-α-olefin copolymers, linear low-density polyethylene resins(L•LDPE), ionomers, polyvinyl butyral resins, silicone resins, andelastomers including polystyrene resins, polyolefine resins, polydieneresins, polyester resins, polyurethane resins, fluorocarbon resins andpolyamide resins.

[1122] The ethylene copolymers may be modified ethylene copolymersproduced through the modification of ethylene copolymers by graftcopolymerization.

[1123] There is not particular restrictions on the thickness of theadhesive layer. The adhesive layer may be formed in a suitable thicknessaccording to the type and shape of the photovoltaic layer provided withsolar cells to which the protective sheet is to be bonded.

[1124] The material for forming the adhesive layer may be prepared in,for example, a solution or a dispersion according to the material andthe thickness of the adhesive layer to be formed, and the adhesive layermay be formed on a surface of the base film by a suitable means, such asa coating process, an extrusion coating process, a calender coatingprocess, a hot lamination process or a dry lamination process.

[1125] The light confinng layer may be formed, for example, in a shapeas shown in FIG. 37(a) or 37(b).

[1126] FIGS. 37(a) and 37(b) are typical sectional views of lightconfining layers for protective sheets in accordance with the presentinvention for solar battery modules. As shown in FIG. 37(a), a lightconfining layer 502 comprises a transparent irregular structure 504formed on one surface (lower surface as viewed in FIG. 37(a)) of a basefilm 501, and a support film 506 provided with an adhesive layer 505,superposed on the irregular structure 504 with adhesive layer 505 facingthe irregular structure 504 and bonded to the irregular structure 504 atbonding spots 510 arranged at predetermined intervals.

[1127] Light scattered outward as indicated by the arrows is reflectedand refracted so as to fall again on solar cells.

[1128] The base film may be provided with a single light confining layersimilar to the light confining layer 502 as shown in FIG. 37(a), twolight confining layers may be formed on the opposite surface,respectively, of the base film or two light confining layers may beformed on one of surfaces of the base film for satisfactory lightconfining effect.

[1129]FIG. 37(b) shows a light confining layer 502 similar to that shownin FIG. 37(a), except that the light confining layer 502 shown in FIG.37(b) has a transparent, composite irregular structure 504 consisting ofa large irregular structure 504 a and a small irregular structure 504 bformed on the surface of the large irregular structure 504 a instead ofthe irregular structure 504 shown in FIG. 37(a).

[1130] As mentioned above, it is preferabvle that each of the irregularstructures 504, 504 a and 504 b is formed by arranging ridges or furrowsof a triangular, trapezoidal or semicircular cross section, projectionsor recesses having the shape of a pyramid, a frustum, a hemisphere, around projection or the like. An irregular structure formed by arrangingpyramidal projections or recesses having intersecting surfaces formingan angle (apex angle) of 90° is particularly preferable.

[1131] Preferably, the height or depth of the irregularities is in therange of 0.1 nm to 500 μm.

[1132] When the irregularities of the irregular structure has arelatively great height or depth in the range of 0.1 μm to 500 μm, theirregular structure can be formed, for example, by heating and softeninga thermoplastic resin layer formed on the base film, pressing anembossing die against the softened thermoplastic resin layer and coolingthe embossed thermopoastic resin layer. Such an irregular structure canbe formed also by applying an ionizing radiation curable resin, such asan ultraviolet curable resin, in a resin film to the base film pressinga separable die or a separable embossing sheet against the film of theionizing radiation curable resin, curing the resin film and separatingthe separable die or the separable embossing sheet from the resin film.

[1133] When the irregularities of the irregular structure has arelatively small height or depth in the range of 0.1 nm to 0.1 μm, theirregular structure can be formed, for example, by forming a transparentZnO ore SnO₂ thin film by a CVD process with etching action or byforming a specular thin film by a CVD process and forming minuteirregularities in the specular thin film by sputtering.

[1134] A transparent SiOx thin film formed by a CVD or a PE-CVD processhas an irregular structure having minute projections. The transparentSiOX thin film serves also as a gas-barrier layer.

[1135] The irregular structure of each of the light confining layers 502shown in FIGS. 37(a) and 37(b) has an air layer to enhance lightreflecting and refracting effect. A transparent material, such as atransparent resin, having a refractive index different from that of thematerial forming the irregular structure or a resin containing dispersedparticles of a transparent material, such as TiO₂ or SiO_(x), having arefractive index different from that of the material forming theirregular structure may be filled in furrows or recesses in theirregular structure to enhance the light reflecting and refractingeffect of the light confining layer.

[1136] When the irregular structure is formed of a resin, a materialhaving a large refractive index in the range of 1.8 to 2.2 or a materialhaving a small refractive index in the range of 1.1 to 1.3 is suitableas the transparent material having a refractive index different fromthat of the material forming the irregular structure.

[1137] When the irregular structure is formed of a resin, a transparentthin film having a refractive index different from that of the materialforming the irregular structure, such as a film of SiO_(x), ZnS, TiO₂ orSb₂O₃, may be formed on the surfaces defining the irregularities of theirregular structure by a deposition means. The transparent thin filmimproves the reflection efficiency of the surface of the irregularitiesto ensure satisfactory light confining effect.

EXAMPLES

[1138] Examples of the eighth embodiment will be explained withreference to the accompanying drawings. The present invention is notlimited in its practical application to examples shown in the drawings.

[1139] A protective sheet (film) in accordance with the presentinvention for a solar battery module is intended to be used as a frontprotective sheet to be bonded to the front surface of a photovoltaiclayer 507 provided with solar cells. The protective sheet is a singleweather-resistant sheet (base film) provided with a light confininglayer or a laminated sheet comprising a plurality of layers including abase film and a light confining layer. FIGS. 35(a) to 35(e) showprotective sheets in accordance with the present invention by way ofexample.

[1140] FIGS. 35(a) to 35(e) are typical sectional views of protectivesheets (protective films) in accordance with the present invention forsolar battery modules. The protective sheet shown in FIG. 35(a)comprises a base film (weather-resistant sheet) 501 and a lightconfining layer 502 a formed on the outer surface of the base film 501,i.e. a surface on the light receiving side of the base film 501. Theprotective sheet shown in FIG. 35(b) comprises a base film(weather-resistant sheet) 501 and a light confining layer 502 a formedon the inner surface of the base film 501, i.e., a surface to belaminated to a photovoltaic layer 507 provided with solar cells.

[1141] The protective sheet shown in FIG. 35(c) comprises a base film(weather-resistant sheet) 501, a light confining layer 502 a formed onthe outer surface of the base film 501, and a light confining layer 502b formed on the inner surface of the base film 501.

[1142] The protective sheets shown in FIG. 35(d) comprises a base film501, a light confining layer 502 b formed on the outer surface of thebase film 501, and a light confining layer 502 a formed on the outersurface of the light confining layer 502 b. The protective sheets shownin FIG. 35(e) comprises a base film 501, a light confining layer 502 aformed on the inner surface of the base film 501, and a light confininglayer 502 b formed on the surface of the light confining layer 502 a.

[1143] When necessary, a gas-barrier layer may be formed on any one ofthe component layers of the protective sheet, preferably, an innerlayer. When a layer other than the base film, such as the lightconfining layer, is the outermost layer, a protective layer may beformed on the surface of the outermost layer by a film laminationprocess or resin coating process.

[1144] As mentioned above, the protective sheet thus formed is excellentin strength, heat resistance, weather resistance, transparency and gasimpermeability, and is capable of making incident light fall repeatedlyon the solar cells and of improving power generating efficiency.

[1145] The protective sheet and a photovoltaic layer provided with solarcells can be laminated by sandwiching a resin film for forming anadhesive layer between the protective sheet and the front surface of thephotovoltaic layer and laminating those component layers by a laminationprocess, in which those component layers are are bonded together by hotpressing.

[1146] A protective sheet in accordance with the present invention for asolar battery module is intended to be used as a front protective sheetto be bonded to the front surface of a photovoltaic layer 507 providedwith solar cells. The protective sheet is a laminated film comprising abase film, an adhesive layer for bonding the protective sheet to aphotovoltaic layer provided with solar cells, and a light confininglayer or the protective sheet is a laminated film comprising a pluralityof layers including a base film, an adhesive layer for bonding theprotective sheet to a photovoltaic layer provided with solar cells, anda light confining layer. FIGS. 36(a) to 36(e) show protective sheets inaccordance with the present invention by way of example.

[1147] FIGS. 36(a) to 36(e) are typical sectional views of protectivesheets (protective films) in accordance with the present invention forsolar battery modules. The protective sheet (protective film) shown inFIG. 36(a) comprises a base film (weather-resistant sheet) 501, a lightconfining layer 502 a formed on the outer surface of the base film 501,i.e. a surface on the light receiving side of the base film 501, and anadhesive layer 503 for bonding the protective sheet to a photovoltaiclayer 507 provided with solar cells formed on the inner surface of thebase film 501, i.e., a surface to be bonded to the photovoltaic layer507.

[1148] The protective sheet shown in FIG. 36(b) comprises a base film(weather-resistant sheet) 501, a light confining layer 502 a formed onthe inner surface of the base film 501, i.e., a surface to be bonded toa photovoltaic layer 507 provided with solar cells, and an adhesivelayer 503 formed on the light confining layer 502 a.

[1149] The protective sheet shown in FIG. 36(c) comprises a base film501 as an outermost layer, an adhesive layer 503 formed on the innersurface of the base film 501, and a light confining layer 502 a formedon the adhesive layer 503. The light confining layer 502 a must beformed so that the periphery thereof lies inside the periphery of theadhesive layer 503 and a peripheral portion of the adhesive layer 503 isexposed to enable the adhesive layer 503 to exercise its bondingfunction.

[1150] The protective sheets shown in FIG. 36(d) comprises a base film501, a light confining layer 502 a formed on the outer surface of thebase film 501, a light confining layer 502 b formed on the inner surfaceof the base film 501, and an adhesive layer 503 formed on the lightconfining layer 502 b.

[1151] The protective sheets shown in FIG. 36(e) comprises a base film501, a light confining layer 502 a formed on the inner surface of thebase film 501, a light confining layer 502 b formed on the surface ofthe light confining layer 502 a, and an adhesive layer 503 formed on thelight confining layer 502 b.

[1152] When necessary, a gas-barrier layer may be formed on any one ofthe component layers of the protective sheet, preferably, an innerlayer. When a layer other than the base film, such as the lightconfining layer, is the outermost layer, a protective layer may beformed on the surface of the outermost layer by a film laminationprocess or resin coating process.

[1153] As mentioned above, the protective sheet thus formed is excellentin strength, heat resistance, weather resistance, transparency and gasimpermeability. Since the protective sheet is provided beforehand withthe adhesive layer for bonding the protective sheet to a photo voltaiclayer provided with solar cells, the adhesive layer can be formed in thelest necessary thickness, and the process for fabricating a solarbattery module is simplified. The protective sheet is capable of makinglight incident on the solar battery module fall repeatedly on the solarcells and of improving power generating efficiency.

[1154] FIGS. 37(a) and 37(b) are typical sectional views of lightconfining layers for protective sheets in accordance with the presentinvention for solar battery modules. These light confining layers arethe same as those previously described with reference to FIGS. 37(a) and37(b) and hence the description thereof will be omitted to avoidduplication.

[1155]FIG. 38(a) is a plan view of an irregular structure of assistancein explaining the irregular structures of the light confining layersshown in FIG. 37(a) and 37(b), FIG. 38(b) is a secitonal view takenonline A-A in FIG. 38(a) and FIG. 38(c) is a perspective view of theirregular structure shown in FIG. 38(a).

[1156] As shown in FIG. 38(c), the light confining layer 502 has acorrugated irregular structure formed by arranging ridges having atriangular cross section. Preferably, the apex angle θ of the triangularcross section of the ridges is about 90°. An optimum apex angle of thetriangular cross section is 90° and a preferable height of thetriangular cross section is in the range of 0.1 nm to 500 μm.

[1157] FIGS. 39(a) is a plan view of another light confining layer 502,FIG. 39(b) is a sectional view taken on line A-A in FIG. 39(a), and FIG.39(9 c) is a perspective view of the light confining layer 502.

[1158] As obvious from FIG. 39(c), the light confining layer 502 shownin FIGS. 39(a) to 39(c) has an irregular structure formed regularlyarranging pyramidal projections. Preferably, the apex angle θ of thetriangular cross section of the pyramidal projections is about 90°. Anoptimum apex angle θ of the triangular cross section of the pyramidalprojection is 90° and a preferable height of the pyramidal projectionsis in the range of 0.1 nm to 500 μm.

[1159]FIG. 40 is a typical sectional view of a solar battery module 500provided with a protective film in accordance with the presentinvention.

[1160] As shown in FIG. 40, the solar battery module 500 is a laminatedstructure comprising a base film 501 as a front surface protectivesheet, a light confining layer 502, an adhesive layer 503, aphotovoltaic layer 507 provided with solar cells, and a substrate 508superposed in that order. The solar battery module may be fabricated,for example, by forming the photovoltaic layer 507 provided with solarcells on the substrate 508, superposing a protective sheet 510 formed bysuperposing and laminating the the base film 501, the light confininglayer 502 and the adhesive layer 503 in that order on the substrate 508provided with the photovoltaic layer 507, and bonding together theprotective sheet 510 and the substrate 508 provided with thephotovoltaic layer 507 by hot pressing.

[1161] When necessary, a gas-barrier layer may be formed on any one ofthe component layers of the protective sheet 510. When necessary, a backsurface protective sheet similar to the protective sheet 510 may bebonded to the back surface, i.e., the outer surface, of the substrate508.

[1162] Since the front surface of the photovoltaic layer provided withsolar cells is covered with the protective sheet excellent in strength,heat resistance, weather resistance, transparency and gas impermeabilityand capable of making light incident on the solar battery module fallrepeatedly on the solar cells, the solar battery module is excellent inlong-term reliability, is capable of effectively using incident lightfallen on the solar cells and has excellent power generating ability.

EXAMPLES

[1163] Examples and a comparative example will be described below.

Example 1

[1164] A 75 μm thick ETFE film was used as a base film. A lightconfining layer having a corrugated irregular structure comprisingridges having a triangular cross section as shown in FIG. 38 was formedof an ultraviolet curable acrylic resin on one of the surfaces of the 75μm thick ETFE film. The triangular cross section was 8 μm in height and60° in apex angle. A 80 nm thick textured layer of ZnO was deposited onthe light confining layer by a CVD process. A 70 nm thick depositedSiO_(x) film as a gas-barrier layer was formed on the textured layer bya CVD process to complete a protective sheet in Example 1 for a solarbattery module.

Example 2

[1165] A protective sheet in Example 2 for a solar battery module of thesame components as those of Example 1 was fabricated by the sameprocesses as in Example 1, except that the protective sheet in Example 2was provided with a light confining layer having a corrugated irregularstructure comprising ridges of a triangular cross section of 8 μm inheight and 90° in apex angle.

Example 3

[1166] A protective sheet in Example 3 for a solar battery module of thesame components as those of Example 1 was fabricated by the sameprocesses as in Example 1, except that the protective sheet in Example 3was provided with a light confining layer having a corrugated irregularstructure comprising ridges of a triangular cross section of 8 μm inheight and 120° in apex angle.

Example 4

[1167] A protective sheet in Example 2 for a solar battery module of thesame components as those of Example 1 was fabricated by the sameprocesses as in Example 1, except that the protective sheet in Example 4was provided with a light confining layer having an irregular structurecomprising pyramidal projections of a triangular cross section of 8 μmin height and 60° in apex angle as shown in FIG. 39.

Example 5

[1168] A protective sheet in Example 5 for a solar battery module of thesame components as those of Example 4 was fabricated by the sameprocesses as in Example 4, except that the protective sheet in Example 5was provided with a light confining layer having an irregular structurecomprising pyramidal projections of a triangular cross section of 8 μmin height and 90° in apex angle.

Example 6

[1169] A protective sheet in Example 6 for a solar battery module of thesame components as those of Example 4 was fabricated by the sameprocesses as in Example 4, except that the protective sheet in Example 6was provided with a light confining layer having an irregular structurecomprising pyramidal projections of a triangular cross section of 8 μmin height and 120° in apex angle.

Comparative Example 1

[1170] A protective sheet in Comparative example 1 for a solar batterymodule of the same components as those of Example 1 was fabricated,except that the protective sheet in Comparative example 1 was providedwith a 8 μm thick flat ultraviolet curable acrylic resin film instead ofthe light confining layer.

[1171] Tests and Test Results

[1172] Solar battery modules in Examples 1 to 6 and Comparative example1 were fabricated by bonding the protective sheets in Examples 1 to 6and Comparative example 1 by hot pressing to photovoltaic layers,respectively. Each photovoltaic layer was provided with amorphoussilicon solar cells formed on a glass substrate provided with adeposited Ag film as a reflecting layer.

[1173] Short-circuit currents J_(sc) (mA/cm²) in the solar batterymodules in Examples 1 to 6 and Comparative example 1 were measured.Percent short-circuit current increase based on the short-circuitcurrent in the solar battery moducle in Comparative example 1 wascalculated. Measured and calculated data are shown in Table 8-1. TABLE8-1 Test Result Short- Short-circuit circuit current Irregular ApexCurrent improvement structure angle (J_(SC) (mA/cm²) ratio (%) Example 1Corrugated 60° 30.5 4.8 Example 2 Corrugated 90° 31.1 6.9 Example 3Corrugated 120°  29.6 1.7 Example 4 Pyramidal 60° 30.8 5.8 Example 5Pyramidal 90° 31.2 7.2 Example 6 Pyramidal 120°  29.3 0.7 ComparativeFlat — 29.1 0   Example 1

[1174] As obvious from Table 8-1, the short-circuit currents in thesolar battery modules in Examples 1 to 6 employing the protective filmsin Examples 1 to 6 as their front surface protective sheets,respectively, are higher than that in the solar battery module inComparative example 1 employing the protective sheets in Comparativeexample 1, which proves the effect of the light confining layer inincreasing short-circuit current.

[1175] The short-circuit current in the solar battery module in Example5 employing the protective sheet provided with the light confining layerhaving the irregular structure formed of the ultraviolet curable resinand comprising the pyramidal projections of a triangular cross sectionof 8 μm in height and 90° in apex angle is the highest and best amongthose in the solar battery modules in Examples 1 to 6.

[1176] As apparent from the foregoing description, the protective sheetaccording to the present invention for a solar battery module isexcellent in strength, heat resistance, weather resistance, transparencyand gas impermeability, and is capable of making light incident on thesolar battery module fall repeatedly on the solar cells to increaseshort-circuit current and power generating efficiency.

[1177] The adhesive layer for bonding the protective sheet to thephotovoltaic layer provided with solar cells can be formed beforehand onthe inner surface of the protective sheet. Therefore, the adhesive layercan be formed in the least necessary thickness and the process forfabricating the solar battery module by bonding together the protectivesheet and the phpotvoltaic layer provided with solar cells can besimplified. The protective sheet makes light incident on the solarbattery module fall repeatedly on the solar cells and thereby increasespower generating efficiency.

[1178] The solar battery module employing the protective sheet as itsfront surface protective sheet or its back surface protective sheet isexcellent in long-term reliability and is capable of generating power ata high power generating efficiency and of being produced at highproductivity.

[1179] The materials mentioned in the description of the first to theseventh embodiment are applicable to the eighth embodiment.

1. A protective sheet for a solar battery module, comprising: aweather-resistant sheet; and a deposited inorganic oxide thin filmformed on one of surfaces of the weather-resistant sheet.
 2. Theprotective sheet for a solar battery module, according to claim 1,wherein the weather-resistant sheet is a fluorocarbon resin sheet. 3.The protective sheet for a solar battery module, according to claim 2,wherein the fluorocarbon resin film has a visible radiationtransmittance of 90% or above.
 4. The protective sheet for a solarbattery module, according to claim 2, wherein the fluorocarbon resinsheet contains an ultraviolet absorber and/or an oxidation inhibitor. 5.The protective sheet for a solar battery module, according to claim 2,wherein a surface-treated layer is formed in one of the surfaces of thefluorocarbon resin sheet.
 6. The protective sheet for a solar batterymodule, according to claim 2, wherein the surface-treated layer is aplasma-processed layer, a corona-processed layer, a layer of a primerfor deposition, a layer of an anchoring agent or a layer of an adhesive.7. The protective sheet for a solar battery module, according to claim2, wherein the deposited inorganic oxide thin film is a single-layerinorganic oxide thin film, a multilayer film consisting of at least twoinorganic thin films or a composite film consisting of at least twodeposited thin films of inorganic oxides different from each other. 8.The protective sheet for a solar battery module, according to claim 1,wherein the weather-resistant sheet is a cyclic polyolefin sheet.
 9. Theprotective sheet for a solar battery module, according to claim 8,wherein the cyclic polyolefin sheet has a visible radiationtransmittance of 90% or above.
 10. The protective sheet for a solarbattery module, according to claim 8, wherein the cyclic polyolefinsheet contains one or some of additives including an ultravioletabsorber, an oxidation inhibitor and reinforcing fibers.
 11. Theprotective sheet for a solar battery module, according to claim 8,wherein a surface of the cyclic polyolefin sheet is processed in anembossed surface.
 12. The protective sheet for a solar battery module,according to claim 8, wherein the deposited inorganic oxide thin film isa single-layer inorganic oxide thin film, a multilayer film consistingof at least two inorganic oxide thin films or a composite filmconsisting of at least two deposited thin films of inorganic oxidesdifferent from each other.
 13. The protective sheet for a solar batterymodule, according to claim 1, wherein a coating film of a compositematerial comprising a condensation polymer produced through thehydrolysis of a silicon compound is formed on the deposited inorganicoxide thin film.
 14. The protective sheet for a solar battery module,according to claim 13, wherein the weather-resistant sheet has a visibleradiation transmittance of 90% or above.
 15. The protective sheet for asolar battery module, according to claim 13, wherein theweather-resistant sheet contains an ultraviolet absorber and/or anoxidation inhibitor.
 16. The protective sheet for a solar batterymodule, according to claim 13, wherein the weather-resistant sheet is afluorocarbon resin sheet, a cyclic polyolefin sheet, a polycarbonatesheet, a poly(meta)acrylic sheet or a polyester sheet.
 17. Theprotective sheet for a solar battery module, according to claim 13,wherein the deposited inorganic oxide thin film is a single-layerinorganic oxide thin film, a multilayer hin film consisting of at leasttwo inorganic oxide thin films or a composite film consisting of atleast two deposited thin films of inorganic oxides different from eachother.
 18. The protective sheet for a solar battery module, according toclaim 13, wherein the deposited inorganic oxide thin film has athickness in the range of 50 to 4000 Å.
 19. The protective sheet for asolar battery module, according to claim 13, wherein the siliconcompound is a substance expressed by a general formula R′SiR₃, where R′denotes a group stable to hydrolysis and capable of being polymerized byheat and/or ionizing radiation, and R denotes an OH group and/or a groupsubject to hydrolysis.
 20. The protective sheet for a solar batterymodule, according to claim 19, wherein R′ in the general formula R′SiR₃is a group including an epoxy atomic group or a group including anatomic group having a C—C double bond.
 21. The protective sheet for asolar battery module, according to claim 19, wherein R′ in the generalformula R′SiR₃ is a group including a (meta)acryl atomic group.
 22. Theprotective sheet for a solar battery module, according to claim 13,wherein the composite material contains a condensation polymer producedthrough the hydrolysis of an organic metal compound expressed by ageneral formula MR_(n), where M denotes an element selected fromsilicon, aluminum, titanium, zirconium, vanadium, boron and tin, Rdenots an OH group and/or a group subject to hydrolysis and n denotesvalence of the metallic element.
 23. The protective sheet for a solarbattery module, according to claim 13, wherein the composite materialcontains a resin having hydrogen bond forming groups.
 24. The protectivesheet for a solar battery module, according to claim 13, wherein theprotective sheet has an oxygen permeability of 2.0 cc/m²•day•atm orbelow in an atmosphere of 25° C. and 90% RH and a moisture permeabilityof 2.0 g/m²•day or below in an atmosphere of 40° C. and 100% RH.
 25. Theprotective sheet for a solar battery module, according to claim 1,wherein a soil-resistant layer and/or an ultraviolet absorbing layer isformed on one of or both the surfaces of the weather-resistant sheet orthe deposited inorganic oxide thin film.
 26. The protective sheet for asolar battery module, according to claim 25, wherein the ultravioletabsorbing layer and the soil-resistant layer are formed on theweather-resistant sheet, and the soil-resistant layer serves as anoutermost layer.
 27. The protective sheet for a solar battery module,according to claim 25, wherein the soil-resistant layer is formed on theweather-resistant sheet, the ultraviolet absorbing layer is formed onthe deposited inorganic oxide thin film, and the soil-resistant layerserves as an outermost layer.
 28. The protective sheet for a solarbattery module, according to claim 25, wherein the weather-resistantsheet is a transparent fluorocarbon resin sheet having a visibleradiation transmittance of 90% or above.
 29. The protective sheet for asolar battery module, according to claim 25, wherein theweather-resistant sheet is a transparent fluorocarbon resin sheet of avinyl fluoride resin or an ethylene-tetrafluoroethylene copolymer. 30.The protective sheet for a solar battery module, according to claim 25,wherein the deposited inorganic oxide thin film is a single-layerinorganic oxide thin film or a multilayer film consisting of at leasttwo inorganic oxide thin films deposited by physical vapor depositionprocesses.
 31. The protective sheet for a solar battery module,according to claim 25, wherein the deposited inorganic oxide thin filmis a single-layer inorganic oxide thin film or a multilayer filmconsisting of at least two inorganic oxide thin films deposited bychemical vapor deposition processes.
 32. The protective sheet for asolar battery module, according to claim 25, wherein the depositedinorganic oxide thin film is a multilayer film consisting of at leasttwo layers formed by a physical vapor deposition process and a chemicalvapor deposition process.
 33. The protective sheet for a solar batterymodule, according to claim 32, wherein the deposited inorganic oxidethin film is a multilayer film consisting of at least a depositedinorganic oxide thin film formed by a chemical vapor deposition processand a deposited inorganic oxide thin film formed by a physical vapordeposition process.
 34. The protective sheet for a solar battery module,according to claim 25, wherein the soil-resistant layer is a coatingfilm of a composite material containing photocatalytic powder containingtitanium oxide as a principal component, or a sol containing fineparticles.
 35. The protective sheet for a solar battery module,according to claim 25, wherein the ultraviolet absorbing layer is acoating film of a composite material containing an ultraviolet absorber.36. The protective sheet for a solar battery module, according to claim1, wherein the a deposition-resistant protective film is sandwichedbetween the weather-resistant sheet and the deposited inorganic oxidethin film.
 37. The protective sheet for a solar battery module,according to claim 36, wherein the weather-resistant sheet has a visibleradiation transmittance of 90% or above.
 38. The protective sheet for asolar battery module, according to claim 36, wherein theweather-resistant sheet contains an ultraviolet absorber and/or anoxidation inhibitor.
 39. The protective sheet for a solar batterymodule, according to claim 36, wherein the weather-resistant sheet is afluorocarbon resin sheet, a cyclic polyolefin sheet, a polycarbonatesheet, a poly(meta)acrylic sheet or a polyester sheet.
 40. Theprotective sheet for a solar battery module, according to claim 36,wherein the deposition-resistant protective film is a depositedinorganic oxide film formed by a chemical vapor deposition process or aphysical vapor deposition process.
 41. The protective sheet for a solarbattery module, according to claim 36, wherein the deposition-resistantprotective film is a deposited inorganic oxide film formed by a plasmachemical vapor deposition process.
 42. The protective sheet for a solarbattery module, according to claim 36, wherein the deposition-resistantprotective film is a deposited silicon oxide film formed by a plasmachemical vapor deposition process.
 43. The protective sheet for a solarbattery module, according to claim 36, wherein the deposition-resistantprotective film is formed of a silicon oxide compound having silicon andoxygen as component elements, and the silicon oxide compound contains atleast carbon or hydrogen as a trace element or both carbon and hydrogenas trace elements.
 44. The protective sheet for a solar battery module,according to claim 36, wherein the deposition-resistant protective filmhas a thickness of 10 Å — than 150 Å.
 45. The protective sheet for asolar battery module, according to claim 36, wherein the depositedinorganic oxide thin film is a single-layer inorganic oxide thin film, amultilayer film consisting of at least two inorganic oxide thin films ora composite film consisting of at least two deposited thin filmsrespectively of different inorganic oxides different from each other.46. The protective sheet for a solar battery module, according to claim36, wherein the deposited inorganic oxide film has a thickness in therange of 150 Å to 4000 Å.
 47. protective sheet for a solar batterymodule, according to claim 1, wherein an additional weather-resistantsheet is disposed on the deposited inorganic oxide thin film.
 48. Theprotective sheet for a solar battery module, according to-claim 47,wherein the weather-resistant sheet has a visible radiationtransmittance of 90% or above.
 49. The protective sheet for a solarbattery module, according to claim 47, wherein the weather-resistantsheet contains an ultraviolet absorber and/or an oxidation inhibitor.50. The protective sheet for a solar battery module, according to claim47, wherein the deposited inorganic oxide thin film is a single-layerinorganic oxide thin film, a multilayer film consisting of at least twoinorganic oxide thin films or a composite film consisting of at leasttwo deposited thin films of inorganic oxides different from each other.51. The protective sheet for a solar battery module, according to claim47, wherein the additional weather-resistant sheet is a cyclicpolyolefin film of a polycyclopentadiene resin, a polydicyclopentadieneresin or a polynorbornadiene resin.
 52. A protective sheet for a solarbattery module, formed by superposing a pair of laminated structureseach comprising a weather-resistant sheet and a deposited inorganicoxide thin film.
 53. The protective sheet for a solar battery module,according to claim 52, wherein the weather-resistant sheet is afluorocarbon resin sheet.
 54. The protective sheet for a solar batterymodule, according to claim 53, wherein the pair of laminated structuresare bonded together with an adhesive layer, an extruded adhesive resinlayer or a resin sheet excellent in strength.
 55. The protective sheetfor a solar battery module, according to claim 53, wherein thefluorocarbon resin sheet has a visible radiation transmittance of 90% orabove.
 56. The protective sheet for a solar battery module, according toclaim 53, wherein the fluorocarbon resin sheet contains an ultravioletabsorber and/or an oxidation inhibitor.
 57. The protective sheet for asolar battery module, according to claim 53, wherein the depositedinorganic oxide thin film is a single-layer inorganic oxide thin film, amultilayer film consisting of at least two inorganic oxide thin films ora composite film consisting of at least two deposited thin films ofinorganic oxides different from each other.
 58. The protective sheet fora solar battery module, according to claim 54, wherein the adhesivelayer, the adhesive layer, the extruded adhesive resin layer or theresin sheet excellent in strength contains an ultraviolet absorberand/or an oxidation inhibitor.
 59. The protective sheet for a solarbattery module, according to claim 52, wherein each of the laminatedstructures has a coating film of a composite material comprising acondensation polymer produced through the hydrolysis of a siliconcompound, formed on the deposited inorganic oxide thin film.
 60. Theprotective sheet for a solar battery module, according to claim 52,wherein the weather-resistant sheet is a cyclic polyolefin sheet. 61.The protective sheet for a solar battery module, according to claim 60,wherein the pair of laminated structures are bonded together with anadhesive layer, an extruded adhesive resin layer or a resin sheetexcellent in strength.
 62. The protective sheet for a solar batterymodule, according to claim 60, wherein the cyclic polyolefin sheet has avisible radiation transmittance of 90% or above.
 63. The protectivesheet for a solar battery module, according to claim 60, wherein thecyclic polyolefin sheet contains an ultraviolet absorber and/oranoxidation inhibitor.
 64. The protective sheet for a solar batterymodule, according to claim 60, wherein the deposited inorganic oxidethin film is a single-layer inorganic oxide thin film, a multilayer filmconsisting of at least two inorganic oxide thin films or a compositefilm consisting of at least two deposited thin films of inorganic oxidesdifferent from each other.
 65. The protective sheet for a solar batterymodule, according to claim 61, wherein the adhesive layer, the extrudedadhesive resin layer or the resin sheet excellent in strength containsan ultraviolet absorber and/or an oxidation inhibitor.
 66. A protectivesheet for a solar battery module, comprising: a weather-resistant sheet;and an ultraviolet intercepting layer, an infrared intercepting layer ora highly reflective layer formed on one of the surfaces of theweather-resistant sheet.
 67. The protective sheet for a solar batterymodule, according to claim 66, wherein the ultraviolet interceptinglayer is a coating resin film containing dispersed metal oxide particleshaving a mean particle size in the range of 1 to 1000 nm.
 68. Theprotective sheet for a solar battery module, according to claim 67,wherein the metal oxide particles are TiO₂ particles, ZnO particles,α-Fe₂O₃ particles or CeO₃ particles.
 69. The protective sheet for asolar battery module, according to claim 66, wherein the infraredintercepting layer is a deposited metal film or a coating resin filmcontaining dispersed metal oxide particles.
 70. The protective sheet fora solar battery module, according to claim 69, wherein the depositedmetal film is a deposited Al film or a deposited Ag film.
 71. Theprotective sheet for a solar battery module, according to claim 69,wherein the metal oxide particles are SnO₂ particles capable ofefficiently absorbing infrared radiation.
 72. The protective sheet for asolar battery module, according to claim 66, wherein the highlyreflective layer is a deposited Ag or Al film, or a resin filmcontaining dispersed white pigment.
 73. A method of fabricating aprotective sheet for a solar battery module, comprising at least aweather-resistant sheet and an ultraviolet intercepting layer formed onthe weather-resistant sheet, said method comprising the steps of:preparing a weather-resistant sheet; and forming an ultravioletintercepting layer by applying a liquid coating resin containingdispersed TiO₂ or CeO₂ particles having a mean particle size in therange of 1 to 1000 nm to the weather-resistant sheet in a coating filmand drying the coating film.
 74. The method of fabricating a protectivesheet for a solar battery module, according to claim 73, wherein aprimer layer is formed on a surface of the weather-resistant sheet onwhich the liquid coating resin is to be applied before applying theliquid coating resin to the weather-resistant sheet.
 75. A method offabricating a protective sheet for a solar battery module, comprising atleast a weather-resistant sheet and an infrared intercepting layerformed on the weather-resistant sheet, said method comprising the stepsof: preparing a weather-resistant sheet; and forming an infraredintercepting layer by applying a liquid coating resin containingdispersed metal oxide particles to the weather-resistant sheet in acoating film and drying the coating film.
 76. A protective sheet for asolar battery module, comprising: a weather-resistant sheet; and a lightconfining layer formed on one of the surfaces of the weather-resistantsheet.
 77. The protective sheet for a solar battery module, according toclaim 76 further comprising an adhesive layer.
 78. The protective sheetfor a solar battery module, according to claim 76, wherein the lightconfining layer has an irregular structure comprising an arrangement ofirregularities having a height or depth in the range of 0.1 nm to 500μm.
 79. The protective sheet for a solar battery module, according toclaim 76, wherein the light confining layer has irregular structurecomprises a large irregular structure comprising an arrangement ofirregularities having a height of depth in the range of 1 to 500 μm, anda small irregular structure comprising small irregularities of a heightor depth in the range of 0.1 to 500 nm formed on the large irregularstructure.
 80. The protective sheet for a solar battery module accordingto claim 76 further comprising a gas-barrier layer.
 81. A solar batterymodule comprising: a photovoltaic layer provided with solar cells; apair of filler layers contiguous respectively with opposite surfaces ofthe photovoltaic layer provided with solar cells; and a pair ofprotective sheets contiguous respectively with the pair of fillerlayers; wherein, at least one of the pair of protective sheets comprisesa weather-resistant sheet and a deposited inorganic oxide thin film. 82.The solar battery module according to claim 81, wherein theweather-resistant sheet is a fluorocarbon resin sheet.
 83. The solarbattery module according to claim 81, wherein the weather-resistantsheet is a cyclic polyolefin sheet.
 84. The solar battery moduleaccording to claim 81, wherein the protective sheet comprising theweather-resistant sheet and the deposited inorganic oxide thin film,further comprises a coating film formed of a composite materialcomprising a condensed polymer produced through the hydrolysis of asilicon compound on the deposited inorganic oxide thin film.
 85. Thesolar battery module according to claim 81, wherein the protective sheetcomprising the weather-resistant sheet and the deposited inorganic oxidethin film, further comprises a soil-resistant layer and/or anultraviolet absorbing layer formed on one of or both the surfaces of theweather-resistant sheet and the deposited inorganic oxide thin film. 86.The solar battery module according to claim 81, wherein the protectivesheet comprising the weather-resistant sheet and the deposited inorganicoxide thin film, further comprises a deposition-resistant protectivefilm sandwiched between the weather-resistant sheet and the depositedinorganic oxide thin film.
 87. The solar battery module according toclaim 81, wherein the protective sheet comprising the weather-resistantsheet and the deposited inorganic oxide thin film, further comprises anadditional weather-resistant sheet disposed on the deposited inorganicoxide thin film.
 88. A solar battery module comprising: a photovoltaiclayer provided with solar cells; a pair of filler layers contiguousrespectively with opposite surfaces of the photovoltaic layer providedwith solar cells; and a pair of protective sheets contiguousrespectively with the pair of filler layers; wherein, at least one ofthe pair of protective sheets comprises a pair of superposed laminatedstructures each comprising a weather-resistant sheet and a depositedinorganic oxide thin film.
 89. The solar battery module according toclaim 88, wherein the weather resistant sheet is a fluorocarbon resinsheet.
 90. The solar battery module according to claim 88, wherein theweather-resistant sheet is a cyclic polyolefin sheet.
 91. The solarbattery module according to claim 88, wherein each laminated structurehas a coating film formed of a composite material comprising a condensedpolymer produced through the hydrolysis of a silicon compound on thedeposited inorganic oxide thin film.
 92. A solar battery modulecomprising: a photovoltaic layer provided with solar cells; a pair offiller layers contiguous respectively with opposite surfaces of thephotovoltaic layer provided with solar cells; and a pair of protectivesheets contiguous respectively with the pair of filler layers; wherein,at least one of the pair of protective sheets comprises aweather-resistant sheet, and an ultraviolet intercepting layer, aninfrared intercepting layer or a highly reflective layer formed on oneof the sufaces of the weather-resistant sheet.
 93. A solar batterymodule comprising: a photovoltaic layer provided with solar cells; apair of filler layers contiguous respectively with opposite surfaces ofthe photovoltaic layer provided with solar cells; and a pair ofprotective sheets contiguous respectively with the pair of fillerlayers; wherein, at least one of the pair of protective sheets comprisesa weather-resistant sheet, and a light confining layer formed on one ofthe surfaces of the weather-resistant sheet.